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1771-6.5.32, Absolute Encoder Module User Manual

1. 1771 DE Let ra Ben Pi oe Pin S D1 1 AN SIE Wi Qe Qe Pin W D1 2 3 SI QI Qa Pin R D1 4 Qis SIG 6 6 Pin K D1 8 Sj 7 7 s Qs Pin E D2 1 9 Cile 0 10 Pin A D2 2 n Sit 2 12 Pin F D2 4 ig NIE Giu Pin B D2 8 Qis OIE 16 J16 Pin G D3 1 Gi GHz Alis SH Pin C D3 2 ji9 Sis C20 IPO e Pins P N V 5V dc SET GM Pins U Z T M signal common Pin X Bi E 5V dc Input Supply 13310 E 5 Appendix Glossary This glossary defines terms pertaining to Allen Bradley Absolute Encoder Modules For abroader glossary of programmable controller words refer to our Programmable Controller Terms publication no PCGI 7 2 ABSOLUTE ENCODER An encoder with a unique digital output code for each increment of shaft rotation BIDIRECTIONAL BLOCK TRANSFER The performance of alternating read and write operations between an intelligent I O module and the processor data table DIFFERENTIAL OUTPUT ENCODER An encoder using differential line driver output devices that have a bit x and bit x output signals ENCODER DATA SETTLING TIME The time required for encoder data to settle to reflect a new position GRAY CODE
2. Left TEE Right Wiring Wiring Arm jaz Arm Pin A GO CC SJ GJ 2 Qe Pin B G1 Sila SIE Qua SIE Pin C G2 ils Qs 6 Qe Pin D G3 Si GI 8 Qs Pin E G4 ile Cile 10 QU Pin F G5 Sn Qt 12 QU t2 Pin G G6 Sis Qh 14 NJi Pin H G7 Jhs Ji QJ he CJ td QI CH17 jrs JH 8 GJ Ito QAH SJ ko Cee e Pin Z 5V dc DA Chat Pin X Sig Com e PNW Ground t 5V dc Input Supply 13309 E 3 Appendix E 0 to 359 count 10 bit BCD Single ended Output Latching E 4 Follow these guidelines The encoder counts up in a counterclockwise direction if you make pin H an open connection or if you connect it to 5V if you connect it to ground the encoder counts up in a clockwise direction Pins P N and V are internally connected on the encoder Pins U Z T and M are internally connected on the encode Encoder output requires 5V DC jumper pins P N and V to pin Y Leave pin L unconnected Ground pin X for normal operation Leave pins J D and Q unconnected Jumper the unused most significant bit input terminals Appendix E Figure E 3 Connection Diagram for Allen Bradley Encoder Bulletin 845C BCD
3. 1 4 1 1 2 1 2 2 0 0 Scanner 3 1 0 4 Make inactive through processor LIST O chassis n number of block transfer modules in chassis Appendix A Active I O channels Block transfer I O channels 2 Block transfer modules on each I O 7 0 1 0 block transfer channel 1 O chassis on each block transfer 5 0 2 0 1 0 channel I O chassis in rack list 2 Determine a time from the table Example values have been added Active I O channels containing one or more block transfer modules 2 67 68 76 3 98 99 4 123 Time ms Number of active I O channels 3 Number of active I O channels containing one or more block transfer modules 2 Time from table 68 ms 3 Compute the scanner times for each block transfer channel Example values have been added CT Channel Time CT Time x BT modules I O chassis 1 x 9 ms table on BT channel on BT channel CT1 68 x 7 5 1 x 9 68 x 7 4 x 9 A 11 Appendix A 476 36 512 ms CT2 Not a block transfer channel CT3 68 x 1 1 x 9 CT4 Notan active channel 4 Compute the encoder read write block transfer time Example values have been added Program Scan Time program 2 5 ms 1K words x 20K words 2 5 x 20 50 ms Scanner Scan Time read or w
4. Current Absolute Position in BCD 13070 The upper byte of 1 indicates the status of the eight outputs controlled by the module The module sets each bit when the corresponding output is turned on Refer to Appendix D for details of these bits The format of the lower byte of word 1 by bit is Programming Example Chapter 4 Module Processor Communication Bit 7 is the loss of input power bit It is set when input power is lost it is reset when power is restored and bit 6 is reset Bit 6 is the write data valid bit It is set at power up and when the processor changes from the program mode to the run mode it is reset when the module receives valid data in a block transfer write operation Bit 5 1s unused Bit 4 is the non BCD preset flag It is set when any preset is in non BCD format Bits 3 through 0 are a binary or hexadecimal code that indicates which preset is not in BCD format Refer to Appendix D for the value of these bits The module identifies each incorrect preset in the order it finds them one at a time Once you correct a preset the module continues to identify any non BCD preset Word 2 indicates the current absolute position of the encoder in BCD Presets are interpreted by the module as absolute numbers to be compared to the absolute position of the encoder shaft they are not interpreted as degrees of shaft rotation Thus if you
5. O O NN DO fF O N O co NOOA O N e NI A c m C Coa La LL a ao e 2 ceeeeemaeaooeeeoooeeoooOoo qoom Hro no a a a a Laai a a La Laa Laat e BG Pin X BLK GND Pin W WHT BLK SIGNAL COM I Pin locations are shown for encoders without colored wires 5V dc Input Supply 13308 E 2 0 to 255 count 8 bit Standard Gray Single ended Output Appendix E Follow these guidelines Set configuration plug E15 on the absolute encoder module to the right position for increasing position Signal common pin X and ground pin W are internally connected on the encoder The encoder counts up in a clockwise direction when you connect pin J instead of pin H Leave pins V and Q unconnected Jumper the unused most significant bit input terminals Figure E 2 Connection Diagram for Allen Bradley Encoder Bulletin 845A Standard Gray
6. Figure 3 7 Differential Output Encoder Connection Diagram Left Right Differential Wiring F1 Wiring Ouput Encoder Arm O Arm Bit 0 n GJ R 9 1 d XX Bit 0 GJ 5 DIE 2 nt I si I N 4 N 4 n Bit 2 Qs Gl Bit 2 m CJ 6 GII e Se d N B N Qs Qs Output HE Qe SI Circuitry bi QU Ito NI to 11 11 Other bit connections not shown Continue in S S this manner until you make all bit connections iie Qe N 13 N 13 N 14 N 14 Gils Sis N 16 g 16 W QJ 17 Bit10 g 18 N 13 Bit 10 From N 19 N 19 Bit11 Encoder N 20 N 20 Bit 11 21 2 If the encoder uses less than 12 bits jumper the unused input terminals t 5V dc Input Supply 12837 Connecting Output Devices Use Figure 3 5 to connect your output devices and supply ies Two output commons are associated with each output group terminals 6 and 7 for outputs 0 through 3 terminals 14 and 15 for outputs 4 through 7 Terminals 6 and 7 are tied together internally as are 14 and 15 so that each output group can use either terminal for that particular group 3 10 Installing the Module Chapter 3 Configuring and Installing Your Module Now that you ve determined the power requirements keying and wiring for your module you can use the following procedure to install it Refer to the Programmable Controller Grounding and Wiring Guidelines pub no 1770 4 1 for proper grounding and wiring methods to install your module WARNING Remove power from the 1771 I O chas
7. word 2 preset A for output 0 word 3 preset B for output 0 word 4 preset A for output 1 word 5 preset B for output 1 4 3 Chapter 4 Module Processor Communication Write Data Throughput Time Block transfer read Data 4 4 Word 1 Output 7 Output 6 Output 5 Output 4 Output 3 Output 2 Output 1 Output 0 Word 2 Thewrite data throughput time is the time between the end of a block transfer write operation and the module update of its outputs The module s response time can vary depending on the number of outputs it controls the type of absolute encoder you use and if you have an offset value The worst case is 4 7 ms Use the following table to determine the module s response time in milliseconds for your application Type of Encoder with or without offset Saas BCD without offset 2 4 6 8 12 1 8 2 5 3 1 BCD with offset Gray code or binary without offset Gray code or binary with offset The processor reads data from the module and transfers it to its data table in two read data words The module sends only two read data words in any one block transfer read operation The format of these words is shown in Figure 4 2 and is described here Figure 4 2 Format of Block transfer read Data 17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00 Status of outputs 0 M S A Code indicating which preset is in non BCD format Non BCD preset flag Unused Write data valid Loss of input power
8. A binary numbering system modified so that only 1 bit changes as the counting number increases MAXIMUM ENCODER SHAFT SPEED The maximum speed at which the encoder shaft can turn to give a one count resolution while controlling a particular number of outputs NEW POSITION THROUGHPUT TIME The time between a certain state being applied to the input terminals and F 1 Appendix F F 2 the appropriate response occurring at the output terminals it depends on the number of outputs the module is controlling NEW WRITE DATA THROUGHPUT TIME The time between the end of a block transfer write operation and the module update of outputs ONE COUNT RESOLUTION The ability of the module to perform within one increment of shaft rotation for example turn on an output at position 007 and off at position 008 PRESET VALUE The value against which the absolute position of the encoder is compared to control an output SINGLE ENDED OUTPUT ENCODER An encoder using single ended totem pole or open collector output devices that have bit x and common output signals Each bit may have a common terminal or all common terminals may be tied to the power supply ground or common terminal in the encoder Symbols Empty 2 1 2 2 3 9 D 1 A Application Considerations B 1 Block tranfer write Data _4 1 Block transfer Timing PLC 2 15 A 7 PLC 2 30 Local System A 4 PLC 2 30 Remote System A 1 PLC 3 A9 Block transfer read Data
9. Allen Bradley Absolute Encoder Module User Manual Cat No 1771 DE Table of Contents Using This Manual leere 1 1 Chapter Objectives 0c cece eee eee eee 1 1 What This Manual Contains 0 00 cece eee aes 1 1 lc P diora keera oh we kaa e se Eo enera 4H Warnings and Cautions a 1 2 SUBITO DV uisi exhi oa REI KADALI EDEN ee Pr LGA 1 2 Introducing the Absolute Encoder Module 2 1 Chapter Objectives aaa 2 1 Example Applications 000s cece eee 2 1 Module Functions 0 000 cece cence eee eens 2 1 Compatible Processors 00 00 cece eee eee e eee 2 2 Compatible Encoders 000 c cece ene n eee eee 2 2 State of Outputs Upon Loss of Input Power 2 2 Module Description 00 a 2 3 Electrostatic Discharge a 2 5 Specifications i xovag kn sek Osaki KAN BG AS ters CI pag 2 46 SUMMA Kabag kaa Kaanak ld gm NG ened ex hawk hcg dee eed 21 Configuring and Installing Your Module 3 1 Chapter Objectives 0 00 cece eee eee 34 Electrostatic Discharge liliis 3 1 Setting Configuration Plugs a 31 Response to External Fault a 3 4 Keying ns nsn Exe er does kA nha hahaa 3 4 Power Requirements 00 00 cece eee een e eens 3 5 Wiring Arm Connections 000 cece cece eens 3 8 Installing the Mod
10. Processor scan time PS 15 ms 1K words Processor I O scan time PIO 5 ms Number of words transferred W 2 read or 20 write 1 Calculate the block transfer time T for the read and write operation T 0 08 ms word x number of words transferred A 7 Appendix A Block transfer Timing for PLC 3 Family Processors A 8 The same equation is used for read and write transfer times 2 Calculate the worst case system time ST between two block transfer read operations ST PS PIO T read PS PIO T write Example 3 A Mini PLC 2 15 programmable controller is communicating with one encoder module in its I O chassis The ladder diagram program contains 2K words Solution The facts are Program length 2K words Processor scan time PS 15 ms 1K words x 2K words 30 ms Processor I O scan time PIO 5 ms Number of words transferred W 2 read 20 write 3 Calculate the block transfer time T for the read and write operation T 0 08 ms word x 2 words read 0 16 ms read T 0 08 ms word x 20 words write 1 6 ms write Calculate the worst case system item ST between two consecutive block transfer read operations ST PS PIO T read PS PIO T write 30 5 16 30 5 1 6 71 76 ms This is the worst case time between two consecutive block transfer read operations for the Mini PLC 2 15 controller The execution time required to complete a block tra
11. Solution Program length 4K words Number of chassis 4 1 assigned rack number per chassis Number of block transfer words W 2 read or 20 write 1 Calculate the system values Processor Scan Time PS 5 ms 1K words x 4K words 20 ms A 6 Appendix A Processor I O Scan Time PIO 0 5 ms rack number x 4 rack numbers 2 ms Number of Words Transferred W 2 read or 20 write 2 Calculate the block transfer times T for the read and write operation T 0 08 ms word x 2 words 16 ms read T 0 08 ms word x 20 words 1 6 ms write 3 Calculate the worst case system time ST between 2 consecutive block transfer read operations The module toggles to a read operation in the scan following completion of the write operation and vice versa ST PS PIO T 1 T 2 TO T 4 writes PS PIO T 1 T 2 T 3 T 4 reads ST 2PS 2PIO 4T read 4T write 2 20 2 2 4 16 4 1 6 40 4 64 6 4 51 04 ms This is the worst case time between two consecutive block transfer read operations in the 4 chassis local configuration described in example 2 one enabled encoder module in each chassis Mini PLC 2 15 Controller The Mini PLC 2 15 scan is 15 ms for 1K program Its I O scan time is 5 ms Each block transfer module is updated during a program scan You can calculate the worst case time between transfers in two steps The facts are
12. one enabled encoder module in each chassis PLC 2 30 Local System The system scan time for a local PLC 2 30 system is the program scan time plus the processor I O scan time Each block transfer module is updated during a program scan The calculation of the worst case time between transfers can be done in three steps Appendix A Calculate the system values that are determined by the system configuration Program Scan PS 5 ms 1K words x number of program words Processor I O Scan PIO 1 ms rack number x number of declared rack numbers Number of words transferred W 2 read or 20 write Calculate the block transfer time T for the read or write operation T 0 08 ms word x number of words transferred Calculate the worst case system time ST between transfers ST PS PIO T 1 read T 2 read T 3 read PS PIO T 1 write T 2 write T 3 write 2 PS PIO T 1 read T 2 read T 3 read T 1 write T 2 write T 3 write Example 2 A PLC 2 30 programmable controller is controlling four I O racks in a local configuration Assume one block transfer module per chassis and one assigned rack number per chassis Figure A 2 A 5 Appendix A Figure A 2 PLC 2 30 Local System Example PLC 2 30 Rack 3 ALINA mo Rack 4 AINA mo 10813 1
13. PLC 2 30 Remote System Example 1772 SD2 PLC 2 30 L4 Rack 2 angas mo Rack 3 mo 108121 1 We want to find the worst case time between two consecutive block transfer read operations from the same module in this system Solution Program length 4K words K 1 024 Number of chassis 4 1 assigned rack number chassis A 3 Appendix A A4 Number of block transfer words 2 words read or 20 words write 1 Calculate the system values Processor Scan Time PS Sms 1K words x 4K words 20ms Processor I O Scan Time PIO 0 5 ms rack number x 4 rack numbers 2 ms Remote Distribution I O Scan Time RIO 7 mx chassis x 4 chassis 28 ms Number of Words Transferred 2 read or 20 write 2 Calculate the block transfer times for a write operation and for a read operation TW PS PIO 2 RIO 0 5W 13 ms 20 2 2 28 0 5 20 13 ms 101 ms write TR PS PIO 2 RIO 0 5W 4 ms 20 2 2 28 0 5 2 4 ms 83 ms read 3 Calculate the worst case system time ST between 2 consecutive block transfer read operations ST 4TW 4TR 4 101 4 83 736 ms This is the worst case time between two consecutive block transfer read operations in the 4 chassis remote configuration described in example 1
14. WARNING Do not remove the wiring arm from an operating module it will cause the power up bit status to change unpredictably until a valid write to the module occurs If swing arm power is lost turn on the power up bit and disable all outputs until a valid write occurs Connecting a Single ended Output Encoder Use Figure 3 6 to connect a single ended output encoder Connect the signal line for bit 0 to terminal 1 of the left wiring arm Connect its return to terminal 2 Connect bit 1 signal line to terminal 3 and its return to terminal 4 Continue in this way for all encoder channels If the encoder has less than 12 signal bits jumper the unused input terminals For example if you are using a 10 bit encoder jumper terminals 19 and 20 and terminals 17 and 18 on the right wiring arm Chapter 3 Configuring and Installing Your Module Figure 3 6 Single ended Output Encoder Connection Diagram Left Right Single ended Wiring Aa Wiring Ouput Encoder Arm Li Arm Bit 0 E GJ 1 GJ 1 XX Common SIE Ql Bit 1 e 5 CH SIE SE
15. _D 2 Block transfer read Data 4 4 C Cabling 3 8 Compatible Encoders 2 2 Configuration Plugs Location Setting 3 3 Settings 3 2 Connections Output Devices 3 10 Power Supplies 3 5 Control Words 4 3 D 1 D Diagnostic Bits D 3 E Encoder 3 9 Format 2 2 3 3 Input Signal Mode 3 3 Example Applications 2 1 F Fuses 2 3 2 ep Index G Glossary F 1 Installation 3 11 K Keying 2 1 34 Module Functions 2 1 module throughput time B 4 O one count resolution _B 1 P Power Requirements Input 2 6 Output 3 5 Output 2 6 3 7 Preset Words 4 3 D 2 Programming Considerations _4 7 Programming Example 4 5 S Specifications 2 6 State of Output Upon Less of Input Power 2 2 Status Indicator 2 3 T Terminal Identification 2 5 Troubleshooting 6 1 IN Rockwell Aviomation Allen Bradley a Rockwell Automation Business has been helping its customers improve productivity and quality for more than 90 years We design manufacture and support a broad Allen Bradley range of automation products worldwide They include logic processors power and motion control devices operator interfaces sensors and a variety of software Rockwell is one of the world s leading technology companies ELA MT dh JS E Hi A gt Worldwide representation m i Argentina e Australia e Austria e Bahrain e Belgium e Brazil e Bulgaria e Canada e Chile e China PRC e C
16. features and hardware components Feature selection and installation procedures Words and file parameters of block transfer data Programming to compensate for shaft offset Troubleshooting guide Instructions for determining block transfer timing Encoder shaft speed Examples of block transfer programming Details of block transfer file data In this manual we assume that you know how to program and operate an Allen Bradley programmable controller program block transfer instructions Chapter 1 Using This Manual If you do not know how to do either of these read the user s manual of your processor Refer to our Publications Index publication SD499 for a complete list of publications Warnings and Cautions Throughout this manual we include special notes to alert you to possible injury to personnel or damage to equipment under specific circumstances WARNING tells you when people may be injured if procedures are not followed properly CAUTION tells you when machinery may be damaged if procedures are not followed properly Summary This chapter told you how to use this manual efficiently The next chapter introduces you to the absolute encoder module Introducing the Absolute Encoder Module Chapter Objectives This chapter describes example applications of the absolute encoder module functions of the module Allen Bradley processors compatible with the absolute encoder module encoders you can
17. ommon Q Q i 2 Bit 2 e N Q E Common m SIE Nle o i rs Ql S7 Qs Qs Output omen d HISIE QI f Circuitry 5i NI ro NI to 11 11 Other bit connections not shown Continue in S S this manner until you make all bit connections iie Qe N 13 N 13 N 14 N 14 Ss Sis N 16 g 16 W QJ 17 Bit10 N Jhs CN te Common From N 19 N 19 Bit11 Encoder QU QJ laf Common 21 2t If the encoder uses less than 12 bits jumper the unused input terminals 5V dc Input Supply 12836 Connecting a Differential Output Encoder Figure 3 7 is the connection diagram for a differential output encoder Connect the bit 0 signal line to terminal and the bit O line to terminal 2 Connect bit 1 to terminal 3 and the bit 1 line to terminal 4 Continue in this way for all encoder channels If the encoder has less than 12 signal bits jumper the unused input terminals For example if you are using a 10 bit encoder jumper terminals 19 and 20 and terminals 17 and 18 on the right wiring arm 3 9 Chapter 3 Configuring and Installing Your Module
18. Although both files appear to be 64 words long only two words are used for read operations and 20 words are used for write operations The remaining words are available for storage File 2600 2700 This is the address of the first word of the read write file Use a file to file move to buffer your read data Use addresses 2500 and 2501 when making data comparisons Rung 4 is entered for display purposes only You do not need this rung in your program it allows you to look at the read and write data files simultaneously Figure C 2 shows example values entered in the read and write data files These values were chosen for a 0 to 359 count BCD encoder Appendix C Figure C 2 Example Read and Write data File PLC 2 Family Processors HEXADECIMAL DATA MONITOR FILE TO FILE MOVE POSITION 001 COUNTER ADDR 060 FILELENGTH 020 FILE A 2600 2623 FILER 2700 2723 POSITION FILE A DATA FILE R DATA 001 0200 9E9E 002 0054 0000 003 0000 0044 004 0000 0045 005 0000 0089 006 0000 9E9E 007 0000 0090 008 0000 0134 009 0000 0135 010 0000 0179 011 0000 9E9E 012 0000 0180 013 0000 0224 014 0000 0225 015 0000 0269 016 0000 9E9E 017 0000 0270 018 0000 0314 019 0000 0315 020 0000 0359 READ DATA WRITE DATA FILE FILE In these file examples word 1 in the read data file indicates output 1 is energized Word 2 indicates that the current encoder position is 054 C 3 Appendix C Thus the current encoder position is between 04
19. Block Transfer Block transfer write Data Module Processor Communication This chapter describes file parameters for the block transfer data files you use to write data to and read data from the absolute encoder module The absolute encoder module and the processor communicate through block transfer programming Processors that use block transfer programming are listed below along with the respective programming manual Refer to the latest edition of the programming manual for a detailed description of block transfer Processor Programming and Operations Manual Publication Number Mini PLC 2 1772 6 8 4 Mini PLC 2 15 1772 6 8 2 Mini PLC 2 05 1772 6 8 6 1772 6 8 1 1772 6 8 3 1772 6 4 1 You write data to the module in blocks You can write 5 10 15 or 20 words in one block transfer operation Each block of five words is associated with two outputs and is identical to each other in format words 1 5 outputs 0 and 1 words 6 10 outputs 2 and 3 words 11 15 outputs 4 and 5 words 16 20 outputs 6 and 7 The first word of each block is a control word The last four words are preset words The formats of the write data words and control word 1 are shown in Figure 4 1 and are described here You can send a maximum of 20 words four block of five words in one block transfer operation The number of words you send to the module determines how many outputs it controls If you want to change data for 4 1 Chapter 4 Modu
20. E2 m E m HE E5 E15 j HE E EB it E9 c E10 T El T E2 Left Board Right 13304 Configuration Plug Settings Gray Encoder Encoder Format Rotational Direction Standard Increasing Decreasing Gray Position Position Chapter 3 Configuring and Installing Your Module Figure 3 2 Configuration Plug Location and Settings Right Board L E1 Down Right Board 13305 Configuration Configuration Plug Settings Plug State of Outputs After Loss of Input Power Supply Selecting Encoder Format and Input Signal Mode Set configuration plugs E1 through E12 on the left board to match the signal mode of each encoder input channel to the encoder Set configuration plugs E13 and E14 also on the left board to match the data format of your encoder Selecting Encoder Rotational Direction Use configuration plug E15 on the left board to indicate the direction of shaft rotation that causes the absolute position to increase for Gray code 3 3 Chapter 3 Configuring and Installing Your Module Response to External Fault Keying 34 encoders This is the same as selecting high true or low true inputs from the Gray encoder Configuration plug E15 is factory set in the right position It gives an increased count when the encoder rotates clockwise when looking at the shaft If your encoder shows a decreased count change the plug to the lef
21. internal components do not touch other circuit components inside the module If available use a static safe workstation When not in use keep the module in its static shield bag 2 5 Chapter 2 Introducing the Absolute Encoder Module Specifications 2 6 damage the module Handle as stated above CAUTION Electrostatic discharge can degrade performance or Module Location Any 1771 1 O chassis any 2 slot 1 O group Number of Inputs Up to 12 encoder input bits per module Encoder Formats BCD Natural binary Standard Gray Digital Resolution Up to one part in 4 095 with natural binary and standard Gray encoders Up to one part in 999 with BCD encoders High true Logic From totem pole open collector or differential line drivers Can select direction of rotation of increasing position for Gray code encoders Input Voltage Range and Logic State Logic 1 1 7V DC Logic 0 0 0V to 0 6V DC Input Current per Channel sunk by encoder device Il mA for single ended drivers l8 mA for differential drivers Maximum input Frequency 50 KHz Encoder Data Settling Time 100 ns Input Power Supply 5V DC 0 25V total output voltage tolerance includes line regulation load regulation drift and ripple Current Requirement 300mA maximum Number of Outputs 8 Output Current Rating 2A sourced per output no derating with all outputs on VA Rating 48W per output 384W per module Surge Rating 4A fo
22. is limited to 5OKHz Appendix Block transfer Ladder Diagram Examples Bidirectional Block transfer for Figure C 1 illustrates the rungs you need to initiate a bidirectional PLC 2 Family Processors block transfer operation using a PLC 2 family processor Figure C 1 Example Block transfer Rungs for PLC 2 Family Processors 047 BLOCK XFERREAD EN DATA ADDR 0050 07 MODULEADDR 470 447 BLOCK LENGTH 02 py FILE 2400 2677 07 147 FILE TO FILE MOVE 0061 IE BUFFER PILE COUNTER ADDR 0061 En o READ DONE BIT POSITION 001 FILE LENGTH 002 FILE A 2600 2601 FILE R 9500 2501 9061 RATEPERSCAN 002 lt DN 15 047 BLOCK XFER WRITE L EN DATA ADDR 0051 06 MODULE ADDR 470 BLOCK LENGTH 00 pN FILE 2700 2777 06 FOR DISPLAY PURPOSES ONLY FILE TO FILE MOVE 0060 COUNTER ADDR 0060 EN POSITION 001 FILE LENGTH 020 17 FILE A 2600 2623 FILE R 2700 2723 bb RATEPERSCAN 020 DN 15 C 1 Appendix C C 2 Data Address 0050 051 This is the first possible address in the timer counter area of the data table Use the first available timer counter address for your first block transfer module data address Module Address 470 The module is located in rack 4 I O group 7 slot 0 Two slot modules are addressed as being in slot 0 Block Length 00 Use the default value for the maximum number of words to read two and write 20
23. or write operation for PLC 2 family processors depends on the system scan time s the number of words to be transferred the I O configuration the number of enabled block transfer instructions in the ladder diagram program during any program scan A block transfer module performs only one block transfer operation per I O scan regardless of whether both read and write operations are requested When done the module toggles from one operation to the other in each program scan For a worst case calculation of the time between block transfers assume that the number of enabled block transfer instructions during any program scan is equal to the number of block transfer modules in the system Also assume that the encoder module is transferring 20 words in a write operation and two words in the alternate read operation The method of calculating the worst case time between block transfers is covered for the following case PLC 2 30 remote and local systems a PLC 3 system and a Mini PLC 2 15 controller PLC 2 30 PLC 2 20 Remote System The system scan time for a remote PLC 2 30 or PLC 2 20 system is the sum of the processor scan time the processor I O scan time between processor and remote distribution panel and the remote distribution panel I O scan time The remote distribution panel can process only one block transfer operation per remote distribution panel scan You can calculate the worst case time between transfers unde
24. terminal 14 or 15 Figure 3 5 Connection Diagram for Output Devices Right F Wiring Arm 1 Output Supply 5 to 24V dc 15 Output Common 5 to 24V dc 4 7 16 Not Used i Bit 10 18 Bit 10 Common 19 Bit 11 20 Bit 11 Common 21 Input Common 5V dc Input circuitry O QJ a Output 0 5 to 24V la Output 1 DC User N 4 Output 2 supply N s Output 3 N e Output Common 5 to 24V dc For Outputs DC Output J 7 Output Common 5 to 24V dc 0 3 Devices N s Not Used N o Output Supply 5 to 24V dc zi QJ lio Output 4 5 to 24V QJ 1 Output 5 DC User Output 6 pny CJ t2 Outpu Jlis Output 7 x Jla Output Common 5 to 24V dc For Outputs N O O N N N See Applicable odes and Laws Tie Wires 12838 Here 3 7 Chapter 3 Configuring and Installing Your Module Wiring Arm Connections 3 8 We recommend the following Belden cable or its equivalent to connect the encoder to the module maximum 50 feet Use extra twisted pairs to connect power to the encoder No of No of Twisted Belden Cable No Encoder Bits Pairs in Cable Important Tighten wiring arm connections to 9 inch pounds of torque
25. use with the module module specifications Example Applications The absolute encoder module is usually used for absolute position feedback high speed response to position based on encoder values immunity to loss of position from power loss or power interruptions Module Functions The Absolute Encoder Module cat no 1771 DE is an intelligent module that provides high speed response to machine position independently of the programmable controller scan It can monitor the position of an absolute encoder that has up to 12 bits control up to eight high current outputs based on comparisons between encoder position and your preset values provide throughput for all eight outputs in less than 200 us communicate with the programmable controller through block transfers return the status of outputs and the position of an absolute encoder to the programmable controller In addition the module can switch 2A DC per output with no derating when all outputs are on allowing 16A continuous per module 2 1 Chapter 2 Introducing the Absolute Encoder Module Compatible Processors Compatible Encoders State of Outputs Upon Loss of Input Power 2 2 You can use the absolute encoder module with any Allen Bradley programmable controller that uses block transfer programming in both local and remote 1771 I O systems Processors that are compatible with the module include Mini PLC 2 cat no 1772 LN3 PLC 2 20
26. value B for output 6 co 19 Preset value A for output 7 20 Preset value B for output 7 Block transfer read Data Read data Words 1 17 Status of output 7 16 Status of output 6 15 Status of output 5 14 Status of output 4 13 Status of output 3 12 Status of output 2 11 Status of output 1 10 Status of output 0 07 Loss of input power bit bit is set when input power is lost it is reset when power is restored and bit 6 is reset D 2 Appendix D 06 Write data valid bit bit is set at power up and when the processor changes from program to run mode it is reset when the module receives valid write data 05 Unused 04 Non BCD preset flag bit is set when any preset is in non BCD format 03 through 00 These bits are binary or hexadecimal code that indicates which of the 16 presets is not in BCD format Refer to the next section for details of these bits 0000 3 0B 1 0001 4 1A 2 0010 5 1B 3 0011 7 2A 4 0100 8 2B 5 0101 9 3A 6 0110 10 3B 7 0111 12 4A 8 1000 13 4B 9 1001 14 5A A 1010 15 5B B 1011 17 6A C 1100 18 6B D 1101 D 3 Appendix D If non BCD Then it is And the Hex And the binary digit is in word preset error code is equivalent is 19 7A E 1110 20 7B F 1111 D 4 Appendix Connection Diagrams for Allen Bradley Encoders Connection Diagrams for Figures E 1 through Figure E 3 show you how to connect several Allen Bradley Encoders Allen Bradley encoders to
27. 06 F LE TO FILE MOVE 0043 UNTERADDR 0043 POSITION 001 AEN FILE LENGTH 022 17 FILE A 0202 0227 9943 FILE R 0200 0225 RATEPERSCAN 022 DN 4 15 5 7 Chapter 5 Offset Programming Rung 1 200 06 and 200 04 are returned in the read operation and latch 077 00 When 077 00 is latched the module toggles between a read operation and a write operation 121 00 is optional and lets the processor initiate a block transfer write operation Rung 2 This rung examines the write done bit 122 06 and the valid BCD data bit 200 04 to unlatch 077 00 and begin the read only operation Rung 3 This rung contains the block transfer read instruction conditioned by the read done bit and the write enable bit 0226 and 0227 when making any data comparisons Rung 4 Use a file to file move to buffer the read data Use addresses Rung 5 This rung contains the block transfer write instruction conditioned by the write done bit and the read enable bit Rung 6 This rung is for display purposes only 5 8 Chapter Objectives Troubleshooting In this chapter you will read how to troubleshoot your absolute encoder module using the ACTIVE GREEN and FAULT red indicators block transfer rungs in your ladder program and diagnostic bits in word 2 of the read data file The following table lists problems indicated by LED changes possible causes and recomended actions LED ON LED OFF Indica
28. 11 This is the address of the first word of the read write file Length 0 Use the default value for the maximum number of words to read two and write 20 CNTL FB010 0040 FB010 0040 This is the address of the block transfer control file C 5 Appendix C Figure C 4 Example Read and Write data Files PLC 3 Processors RADIX H START WB015 0000 WORD 0 1 2 3 4 5 6 7 00000 0000 0200 0693 0000 0000 0000 0000 0000 00008 0000 0000 0000 9E9E 0000 0511 0512 1023 00016 9E9E 1024 1535 1536 2047 9E9E 2048 2559 00024 2560 3071 9E9E 3072 3583 3584 4095 0000 00032 0000 0000 0000 0000 0000 0000 0000 0000 00040 In this example Word 1 shows that output 1 is energized Word 2 indicates the current encoder position is 693 The current position is between the presets for output 1 words 14 and 15 Read only Block transfer for Figure C 5 shows example rungs for a read only block transfer operation PLC 2 Family Processors Use this example to optimize your block transfer timing C 6 Appendix C Figure C 5 Example Read only Block transfer Program for PLC 2 Family Processors LADDER DIAGRAM DUMP 200 START 077 H E Se POWER UP BIT 06 OFF00 200 4 WRITE DATA VALID BIT 121 00 PUSHBUTTON TO CHANGE PRESETS 122 200 077 ue E U 06 04 OFF00 022 BLOCK XFER READ EN DATA ADDR 0040 07 MODULE ADDR 220 122 BLOCK LENGTH 00 py FILE 0
29. 200 0277 07 READ FILE DONE DONE BIT BIT FILE TO FILE MOVE 0044 ie a BUFFER FILE COUNTERADDR 0044 EN JE Vt POSITION 01 4 07 15 FILE LENGTH 002 FER 0206 0207 OOM H _ RATEPERSCAN 002 hae 077 022 WRITE ENABLE BIT JE BLOCK XFER WRITE EN 00 DATA ADDR 0041 06 MODULE ADDR 220 122 BLOCK LENGTH 00 py FILE 0202 0301 06 FILE TO FILE MOVE 0043 COUNTER ADDR 0043 HEN POSITION 001 47 FILE LENGTH 020 FILE A 0202 0225 0043 FILE R 0200 0223 DN RATE PER SCAN 020 K V This example is a read only operation Use it to increase the PC s update time of the module s status C 7 Appendix C Rung 1 200 06 and 200 4 are returned in the read operation and latch 077 00 When 077 00 is latched the module toggles between a read operation and a write operation 121 00 is optional and lets the processor initiate a block transfer write operation Rung 2 This rung examines the write done bit 122 06 and the valid BCD data bit 200 04 to unlatch 077 00 and begin the read only operation Rung 3 This rung contains the block transfer read instruction Rung 4 Use a file to file move to buffer the read data Use addresses 0226 and 0227 when making any data comparisons Rung 5 A block transfer write is not done unless 077 00 is on Rung 6 This rung is for display purposes only C 8 Block transfer write Data Appendix Bit and Word Descriptions of Block transfer Data Con
30. 5 and 089 words 4 and 5 which are the presets for output 1 Bidirectional Block transfer for Figure C 3 shows you how to program a bidirectional block transfer PLC 3 Processors operation using a PLC 3 processor Figure C 4 gives example values entered in the write data files and displayed in the read data files The values were chosen for use with a single ended 0 to 4 095 count binary encoder Figure C 3 Example Block transfer Rungs for PLC 3 Processors WB010 0040 BTR CNTL E BLOCK XFER READ EN n READ DONE BIT RACK 002 pua GROUP 3 CNTL MODULE 0 LOW DN DATA FB015 0001 45 LENGTH 0 CNTL CNTL FB010 0040 ER READ REQUEST 13 WB010 0040 BTW CNTL p BLOCK XFER WRITE EN 17 RACK 002 go GROUP 3 CNTL MODULE 0 LOW DN DATA FB015 0011 95 LENGTH 0 CNTL CNTL FB010 0040 ER 03 WB010 0040 BUFFER FILE MVF C0110 jun FILES FROMA TO R EN 1 E J 15 12 A FB015 0001 C0110 R FB016 0001 DN COUNTER Cotto 2 POSILEN 0 2 corto MODE ALL SCAN ER 13 C4 Appendix C Use a file to file move to buffer the read data Use B016 0001 status and B016 0002 position for all data comparisons Rack 002 The module is located in rack 2 Group 3 The module is located in I O group 3 Module 0 low The module is in the low slot of the I O group Two slot modules are addressed as being in slot 0 Data FB015 0001 FB015 00
31. Common Bit 1 Bit 1 Common Bit 2 Bit 2 Common Bit 3 Bit 3 Common Bit 4 Bit 4 Common B5 Bit 5 Common Bit 6 Bit 6 Common Bit 7 Bit 7 Common B8 Bit 8 Common Bit9 Bit 9 Common Input Supply 5V dc Output Supply 5 to 24V dc Output 0 Output 1 Output 2 Output 3 Output Common 5 to 24V dc For Outputs Output Common 5 to 24V dc 0 3 Not Used Output Supply 5 to 24V dc Output 4 Output 5 Output 6 Output 7 Output Common 5 to 24V dc For Outputs Output Common 5 to 24V dc 4 7 Not Used Bit 10 Bit 10 Common Bit 11 eaoodoeoo UukccoooooooooOtC aeeaeeaaeaeoaeeoeaeeeaeoo Bit 11 Common Input Common 45V dc 12832 Electrostatic discharge can damage integrated circuits or semiconductors in this module if you touch backplane connector pins It can also damage the module when you set configuration plugs or switches inside the module Avoid electrostatic discharge by observing the following precautions Touch a grounded object to discharge yourself before handling the module Do not touch the backplane connector or connector pins When you configure and replace
32. able the rung containing the alternate instruction until the done bit of the first transfer is set If you enable them in the same scan the number of words transferred may not be the number intended invalid data could be operated upon in subsequent scans or output devices could be controlled by invalid data Unexpected and or hazardous machine operation could occur Damage to equipment and or personal injury could result This chapter gave a description of the file parameters for programming block transfer read and write operations for the absolute encoder module It also gave several programming examples and considerations for use with the absolute encoder module The next chapter describes troubleshooting the module 4 7 Offset Feature Offset Feature Offset is a new feature of the Absolute Encoder Module cat no 1771 DE revision B Revision A modules do not have this feature Offset is the difference between the 0 position of the absolute encoder and the O position of the machine shaft to which the encoder is connected You can program this value to compensate for such factors as machine wear or improper mechanical setup You do not have to disconnect your equipment to realign the O position of the machine shaft with the 0 position of the absolute encoder Determining the Offset Value You can find the offset value using either of two equations depending on whether you use the 0 machine position or the 0 encoder position
33. as your reference To calculate an offset value from a 0 encoder position use this equation N M S where N number of encoder positions M machine position at encoder 0 and S offset To calculate an offset value from a 0 machine position use this equation E N S where E encoder position at machine 0 N number of encoder positions and S offset Let s look at an example finding the offset value with reference to 0 encoder position and 0 machine position Assume the following You have a 0 to 4 095 position encoder 4 096 positions The machine shaft is at position 512 when the encoder is at position 0 The encoder is at position 3 584 when the machine is at position 0 5 1 Chapter 5 Offset Programming Offset Words 5 2 In this example the 0 machine position is ahead of the 0 encoder position Depending on which equation you use your reference point the offset value is either positive or negative Offset Value From 0 Encoder Position and From 0 Machine Position 0 3584 Encoder 512 4 Machine shaft At encoder position 0 machine shaft position is 512 The offset is 43 584 At machine shaft position 0 encoder position is 3 584 The offset is 512 13522 The equation from 0 encoder position is 4 096 512 2 3 584 The offset is 3 584 The equation from 0 machine position is 3 584 4 096 512 The offset is 512 You get the same result from programming eithe
34. associated with two outputs The lower byte of control word 1 is associated with output 0 Its format is as follows Bits 0 through 2 are the comparison bits for output 0 preset A greater than less than equal to greater than or equal to less than or equal to Bits 3 through 5 are the comparison bits for output 0 preset B Bit 6 is the zero transition ZT bit Set this bit when an output is to be energized during a transition through 0 Bit 7 is the output enable OE bit This bit is examined along with the comparison made by the module between your presets and the absolute position of the encoder in turning on a module s output Although comparisons to the presets may be true if you don t set this bit the output is not turned on The upper byte of control word 1 is associated with output 1 The format of this byte is similar to the format of the lower byte Bits 10 through 12 are the comparison bits for output 1 preset A Bits 13 through 15 are the comparison bits for output 1 preset B Bit 16 is the ZT bit Bit 17 is the OE bit The remaining control words with their corresponding outputs are word 6 outputs 2 and 3 word 11 outputs 4 and 5 word 16 outputs 6 and 7 Preset Words The present words define preset values for turn on and turn off points of the corresponding output You program them in BCD Each block of four preset words is associated with two outputs and is identical in format to that for outputs O and 1
35. cat no 1772 LP1 LP2 PLC 2 30 cat no 1772 LP3 PLC 3 cat no 1775 L1 L2 Mini PLC 2 15 cat no 1772 LV Mini PLC 2 05 cat no 1772 LS LSP You can use Allen Bradley absolute encoders that use up to 12 bits with the absolute encoder module Allen Bradley encoders with the following bulletin numbers are compatible with the absolute encoder module Bulletin 845A Bulletin 845B Bulletin 845C The module is also compatible with absolute encoders that have the following specifications single ended or differential encoder output signals TTL compatibility output drivers capability of sinking 11mA single ended or 18mA differential per channel BCD natural binary or standard Gray code format You can select the state in which the outputs will be if the module loses input power A configuration plug on the right printed circuit board allows the outputs to turn off remain in their state at loss of input power Chapter 2 Introducing the Absolute Encoder Module Module Description The next four sections give a description and specifications of the absolute encoder module Status Indicators The module has 10 LED status indicators Figure 2 1 Eight output status indicators one for each output light when the corresponding output circuitry is energized One green ACTIVE indicator lights when the module is powered and functioning One red FAULT indicator lights when the m
36. comparison A or comparison B is true Let s continue this example and assume your application requirements for outputs 0 and 1 are output 0 is to turn on at position 330 and turn off at position 005 output 1 is to turn on between position 007 and position 011 Once you define the presets for outputs O and 1 determine the comparison bits for each preset and enter the data into the data file the block of data you write to the module five words looks like this 17 16 15 14 13 12 11 10 07 06 05 04 03 02 o1 oo Bit 4 6 Control Word Function Control Word Preset 0A Preset 0B Preset 1A Preset 1B Programming Considerations Summary Chapter 4 Module Processor Communication When you specify the default block length 00 the following considerations apply for PLC 2 family processors You can and should enable the read and write instructions in the same scan separate but equal input conditions The module decides which operation is performed first when both instructions are enabled in the same scan Alternate operation is performed in a subsequent scan Do not operate on transferred data until the done bit is set When you examine the read and write files 64 words appear to be moved however the processor writes only 20 words and reads only two words in any block transfer operation WARNING When the block lengths of bidirectional block transfer instructions are set to unequal values do not en
37. e the read and write instruction in the same scan Your conditioning instructions in block transfer rungs allow the rungs to turn off and on f you re using a PLC 2 30 processor set the scanner for block transfer operation If you re using a PLC 3 processor create block transfer data files Examine the diagnostic bits by displaying the read block of the block transfer read instruction Refer to the programming manual of your processor for the procedure The lower byte of the first read data word contains the diagnostic bits The module is not receiving 5V from the input power supply check the supply and the connections between the supply and the module The module has not received any block transfer write data check your block transfer instructions The module has examined all 16 presets it has received write data and has found a preset that is not in BCD check bits 03 through 00 for the error code to determine which word contains the incorrect preset See Appendix D for the error codes If you have followed the wiring and installation guidelines in chapter 3 and the block transfer guidelines in chapter 4 you have minimized the need to troubleshoot your encoder module If you need to troubleshoot however the information in this chapter can help you diagnose and correct problems Block transfer Timing for PLC 2 Family Processors Appendix Block transfer Timing The time required for a block transfer read
38. er Data Block transfer write Data 2 ee eee Block transfer read Data cece eee eee eee eae Connection Diagrams for Allen Bradley Encoders Connection Diagrams for Allen Bradley Encoders 0 to 359 count 10 bit BCD Single ended Output 0 to 255 count 8 bit Standard Gray Single ended Output 0 to 359 count 10 bit BCD Single ended Output Latching Glossary PP PREP PEP POP DP PP PAP APAPAP PAA PAT Cc 1 Hare m pana idi no Sa Dx D 1 Hara iud hbd P no p no P T a 6o UN iN e LI hk ily he AB O D o LI T T n5 m O m Ln m m Ko m AB Chapter Objectives What This Manual Contains Chapter Appendix 1 2 Audience Using This Manual Read this chapter to familiarize yourself with this manual It tells you how to use the manual properly and efficiently This manual contains 5 chapters and 6 appendices Title Using This Manual Introducing the Absolute Encoder Module Configuring and Installing Your Module Module Processor Communication Offset Feature Troubleshooting Block transfer Timing Application Consideration Block transfer Ladder Diagram Examples Biat and Word Description of Block transfer Data Glossary Index What s Covered Manual s purpose audience and contents Module description
39. erving the following precautions Touch a grounded object to discharge yourself before handling the module Do not touch the backplane connector or connector pins When you configure and replace internal components do not touch other circuit components inside the module If available use a static safe work station When not in use keep the module in its static shield bag CAUTION Electrostatic discharge can degrade performance or damage the module Handle as stated above You can choose various module features by setting configuration plugs The module is factory set for use with a BCD differential output encoder To access the configuration plugs lay the module on its right side and remove the cover The configuration plug sockets are labeled E1 through E15 on the left printed circuit board and E1 on the right printed circuit board Locate the configuration plugs with the board positioned as shown in Figure 3 1 and Figure 3 2 Each plug is inserted on two pins of a three pin connector You change the position of the plugs in a left right or up down direction 3 1 Chapter 3 Configuring and Installing Your Module Figure 3 1 Configuration Plug Locations and Settings Left Board Config uration through E12 3 2 ie E13 E14 Encoder Signal Differ ential x_ _ El na X
40. evolution per second Control is easily maintained over a one count resolution and the output appears to follow the input more closely In both examples the module throughput time is the same depending only on the number of outputs to be controlled see table below But with increasingly lower input frequencies slower shaft speed the delay from change in input to output control is smaller compared to the input period of an encoder increment Appendix B When New Position Controlling Throughput Time is 4 outputs 111 us You must take into account the fixed throughput time the number of outputs per module and the number of increments between the preset values when determining the appropriate machine preset values for a design shaft speed Due to the effects shown in the first example you may want to adjust the preset values to account for the throughput time This is important if the module is used near its maximum design speed If the maximum encoder shaft speed determined from the above equations is too slow for your application you should consider the following If you increase the input speed slightly you can still maintain control to a one count resolution However the encoder position value and the output status read by the PC may not correspond If for example you request an output to turn on at position 100 for one PC scan the PC might see a position value of 099 while the output on bit is set The comparisons
41. have a 0 to 999 position encoder you program presets for output 3 for example as Preset 3A 200 Preset 3B 402 There is no restriction on which mode of comparison you can use for preset A or preset B In this example we assume the use of a 0 to 359 position encoder when referring to degrees of shaft rotation If you want to turn on output O between shaft positions 330 preset A and 005 preset B you set the greater than and equal to bits for preset A the less than and equal to bits for preset B the ZT bit 4 5 Chapter 4 Module Processor Communication the OE bit Output 0 is turned on when the shaft position is greater than or equal to 330 or when the shaft position is less than or equal to 005 If you don t set the ZT bit in the above control word when the encoder shaft position is 002 for example comparison B is true comparison A is not true and the output is turned off At position 002 the shaft position is less than or equal to 005 but it is not greater than or equal to 330 You must set the ZT bit when an output is to be energized during a transition through 0 Another way to energize output 0 between position 330 and 005 is to give preset A a value of 006 and preset B a value of 329 Then you set the less than bit for preset A the greater than bit for preset B the ZT bit OE bit In either case you must set bit 6 ZT to indicate that the output should be on if either
42. ing bands must correspond to these slots to allow insertion of the module Position the keying bands on the upper backplane connector between the numbers at the right of the connectors Keying bands are only used to key slot 0 of the module Figure 3 3 illustrates the encoder module keying positions for slot 0 Figure 3 3 Keying Positions Upper Backplane Connectors 2 slot I O group Keying 12 12 Bands 14 14 Left Right 12834 Connector Connector You must provide a minimum of two external power supplies one to power input circuitry and one to power output devices Input Power Supply Connect a 5V DC power supply for the input circuitry between terminal 2 of the left wiring arm and terminal 21 of the right wiring arm Make sure the voltage is 5V DC 25V The input circuitry requires a 3 5 Chapter 3 Configuring and Installing Your Module 3 6 maximum of 300mA For the best system noise immunity we recommend use of a separate linear regulated power supply for powering the input circuitry and the encoder You can use this supply for more than one absolute encoder module or encoder but do not use it for otehr 5V loads such as relays Make sure the power supply has enough additional current capacity for the encoder We suggest you use extra shielded twisted pairs of wire in the encoder input cable to power the encoder If more than one extra pai
43. le Processor Communication outputs 4 and 5 and the module is controlling all eight outputs you must send 20 words to the module you cannot send only the words associated with outputs 4 and 5 Figure 4 1 Format of Block transfer write Data 17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00 gt 7 B Control word Word 1 OE ZT gt lt gt lt OE ZT for Outputs 0 and 1 2 Preset 0A 3 Preset 0B 4 Preset 1A 5 Preset 1B m Control word 6 OE ZT gt lt gt lt OE ZT gt lt go Outputs 2 and 3 7 Preset 2A A Write data Words 8 Preset 2B 9 Preset 3A 10 Preset 3B z a B Control word N OE ZT j5 c 2 lt JOE ZT 5 lt toe Outputs 4 and 5 12 Preset 4A 13 Preset 4B 14 Preset 5A 15 Preset 5B 5 5 Control word 16 0E ZT gt 2c gt f lt OE ZT gt lt fr Outputs 6 and 7 17 Preset 6A 18 Preset 6B 19 Preset 7A 20 Preset 7B COM for COM for COM for COM for Preset 1B Preset 1A Preset 0B Preset 0A B Format of Control 2 Word 1 OE ZT 2 2 lt OEZT 2 2 OE Output Enable Bit ZT Zero Transition Bit COM Comparison Bits 12839 4 2 Chapter 4 Module Processor Communication Control Words Each control word is
44. nsfer read or write operation with a PLC 3 family processor depends on the number of words of user program active I O channels on the scanner Appendix A I O chassis entries in the rack list for the channel I O channels on the scanner that contain bloc transfer modules block transfer modules on the channel if the I O chassis containing a block transfer module appears more than once in the I O chassis rack list count the module once each time the chassis appears in the rack list The typical time required for the encoder module to complete a block transfer read write bidirectional depends on the program scan and the scanner scan as follows Time read write program scan 2 scanner scan Program Scan The program scan is approximately 2 5 ms per 1K words or user program when using examine on off and block instructions Scanner Scan The time required for the scanner to complete a re or write block transfer depends on the number of other block transfer modules on the same scanner channel that are enabled simultaneously Block transfer times typically are similar regardless of the type of block transfer module the number of words transferred or whether a read or write operation is requested A block transfer I O channel is a channel that contains one or more block transfer modules located in any chassis connected to the channel An I O chassis can appear more than once in a rack list of I O chassis Coun
45. nt of shaft rotation This bit has the highest input frequency of all encoder channels because it changes state most often Although the LSB on standard Gray encoders does not toggle with each increment in shaft position circuitry on the module converts the Gray code to binary code to be used by the module B 3 Appendix B B 4 The second waveform represents the new position throughput time of the module The third waveform represents an output programmed to turn on an actuator device waveform high when the encoder position is 000 and to turn it off waveform low when the encoder position is 001 The new position throughput time of the module is based on the following sequence of events a The encoder shaft increases one position b All 16 presets are compared to the encoder position c The module updates the outputs d The outputs are in the correct state for the given position and the scan period is complete e The module scan begins with the next increase in the encoder shaft position and the process then repeats Let s look at the first example where the encoder is operating near maximum speed and control is maintained over a one count resolution Comparing the input and output waveforms the output bit comes on when the encoder position is almost 001 and turns off when the position is almost 002 This is due to the time needed for the software comparison The second example shows waveforms for a speed of one r
46. odule detects a fault and momentarily lights at power up Figure 2 1 Status Indicators li amp Status Indicators Active ABSOLUTE 0 ENCODER 1 MODULE 2 3 Output status E B 4 Indicators 5 ISI IV 6 7 N S Fault S S GI g S S S g g S S S g g S S G S g S fi sl jm Output Fuses The module has eight 3A rectifier fuses one per output located on the right printed circuit board Figure 2 2 shows the fuse locations 2 3 Chapter 2 Introducing the Absolute Encoder Module Figure 2 2 Fuse Locations Fi F2 F3 F4 F5 F6 F7 F8 Right Board 13303 Terminal Identification Figure 2 3 identifies each terminal of the absolute encoder module The bit x common terminals refer to not bit x terminals uses with differential output encoders Or common terminals used with single ended output encoders 24 Electrostatic Discharge Figure 2 3 Terminal Identification Left Wiring Arm Chapter 2 Introducing the Absolute Encoder Module Right Wiring Arm Bit 0 Bit 0
47. olombia e Costa Rica e Croatia e Cyprus e Czech Republic e Denmark e Ecuador e Egypt e El Salvador e Finland e France e Germany e Greece e Guatemala e Honduras e Hong Kong e Hungary e Iceland e India e Indonesia e Ireland e Israel e Italy e Jamaica e Japan e Jordan e Korea e Kuwait e Lebanon e Malaysia e Mexico e Netherlands e New Zealand e Norway e Pakistan e Peru e Philippines e Poland e Portugal e Puerto Rico e Qatar e Romania e Russia CIS e Saudi Arabia e Singapore e Slovakia e Slovenia e South Africa Republic e Spain e Sweden e Switzerland e Taiwan Thailand e Turkey e United Arab Emirates e United Kingdom e United States e Uruguay e Venezuela e Yugoslavia Allen Bradley Headquarters 1201 South Second Street Milwaukee WI 53204 USA Tel 1 414 382 2000 Fax 1 414 382 4444 Publication 1771 6 5 32 January 1986 PN 955096 76 Copyright 1986 Allen Bradley Company Inc Printed in USA
48. outputs 17 words If the module is controlling eight outputs your block transfer write data now looks like this 5 3 Chapter 5 Offset Programming Figure 5 1 Format of Block transfer write Data with Offset 17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00 e p 2 Control Word for Word 1 OE ZT gt lt gt 2 QE ZT gt lt gt lt Outputs 0 and 1 2 Preset 0A 3 Preset 0B 4 Preset 1A 5 Preset 1B i S _ Control Word for 6 OE ZT gt lt gt lt OE ZT gt lt gt Outputs 2 and 3 7 Preset 2A 8 Preset 2B 9 Preset 3A 10 Preset 3B A Write data words C a ontrol Word for 11 OE ZT 5 5 5 3 c 0E ZF 3 5 6 2 Outputs 4 and 5 12 Preset 4A 13 Preset 4B 14 Preset 5A 15 Preset 5B T T _ Control Word for 16 OEZT gt lt gt lt OE ZT gt lt gt lt Outputs 6 and 7 17 Preset 6A 18 Preset 6B 19 Preset 7A 20 Preset 7B 21 S Offset Value 22 No of Encoder Positions COM for COM for COM for COM for Preset 1B Preset 1A PresetOB Preset 0A B Format of control word 1 OE ZT gt lt gt lt OE ZT gt 5 z x OE Output Enable Bit ZT Zero Transition Bit COM Comparison Bit 10698 1 S Offset Sign Bit Block transfer read Data with Offset The up
49. per byte of word 1 indicates the status of the eight outputs controlled by the module The module sets each bit when the corresponding output is turned on The lower byte of word 1 by bit is 5 4 Word 1 Output 6 Output 5 Output 4 Chapter 5 Offset Programming Bit 7 is the loss of input power bit It is set when input power is lost it is reset when power is restored and bit 6 is reset Bit 6 is the write data valid bit It is set at power up and when the processor changes from program mode to run mode it is reset when the module receives valid data in a block transfer write operation Bit 5 is the non BCD offset flag See the description of bit 0 and bit 1 below to identify the type of offset error Bit 4 is the non BCD preset flag It is set when a preset word is in non BCD format Bits 3 through 0 are a binary or hexadecimal code that indicates which preset word is not in BCD format Refer to Appendix D of the User s Manual for the value of these bits Bit 1 when set along with bit 5 identifies that the offset value is greater than the number of encoder positions Bit 0 identifies which offset word is in non BCD format when bit 5 is also set If bit O is set the word containing the number of encoder positions is in error If bit 0 is reset the word containing the offset value is in error The module identifies each non BCD word in the order it finds them one at a time Once you correct
50. r 43 584 or 512 Once you determine the offset value you need to program two write block transfer words These are the last two words of the write data block that you send to the absolute encoder module You program them in BCD as you do the preset values Chapter 5 Offset Programming Format of Offset Words rn 107 fe s 4 o Jo 1 Jo Bt OFFSET VALUE S NO OF ENCODER POSITIONS The offset words are the last two words of the write data block that you send to the absolute encoder module If you are controlling The offset words are 2 outputs words 6 and 7 4 outputs words 11 and 12 6 outputs words 16 and 17 8 outputs words 21 and 22 S sign bit Set this bit if the offset has a negative value reset the bit if the offset has a positive value 13523 The first offset word contains the value of the offset Bit 17 of this word is the sign bit It indicates whether the offset is negative or positive Set bit 17 if the offset is negative reset it if the offset is positive The second offset word is the number of positions of the encoder If you are using a 0 to 4 095 position encoder your second offset word is 4 096 Block transfer write Data with Offset The number of words you send to the module depends on the number of outputs the module controls The offset feature adds two words to the total number of words you send to the module If the module controls 2 outputs 7 words Foutputs 2wods 6
51. r I0 ms Input and Output Isolation 1500V RMS Output Power Supply Selectable 5 to 24V DC Backplane Current 800 mA at 5V DC Output Fuses 3A rectifier fuses Littelfuse 322003 Buss GBB003 or equivalent Summary Chapter 2 Introducing the Absolute Encoder Module New Position Throughput Time Environmental Conditions 200 us Operating Temperature 0 to 60 C 32 to 140 F Storage Temperature 40 to 85 C 40 to 185 F Relative Humidity 5 to 9596 without condensation New Write data Throughput Time Keying for slot 0 only 4 7 ms Between 2 and 4 Between 26 and 28 Torque for wiring arm connections 9 inch pounds This chapter described the absolute encoder module its functions and applications and the processors and encoders with which it is compatible The next chapter tells you how to configure and install the module 2 7 Chapter Objectives Electrostatic Discharge Setting Configuration Plugs Configuring and Installing Your Module This chapter tells you how to select module features by setting configuration plugs power module input circuitry and output devices key the module make wiring arm connections install the module Electrostatic discharge can damage integrated dircuits or semiconductors in this module if you touch backplane connector pins It can also damage the module when you set configuration plugs or switches inside the module Avoid electrostatic discharge by obs
52. r normal operating conditions in three steps 1 Calculate the system values that are determined by the system configuration A 1 Appendix A Program Scan PS 5 ms 1K words x number of program words Processor I O Scan PIO 0 5 ms rack number x declared rack numbers Remote Distribution I O Scan RIO 7 ms chassis x number of chassis Number of Words Transferred W 20 words for one write operation two words for one read operation 2 Calculate the block transfer time for a write operation TW and for a read operation TR TW PS PIO 2 RIO 0 5W 13 ms TR PS PIO 2 RIO 0 5W 4 ms These equations are valid for up to 10 000 cable feet between the remote distribution panel and remote I O chassis for a baud rate of 57 6kBd or 5 000 cable feet at 115kBd 3 Calculate the worst case system time ST between transfers ST Sum of transfer times of all block transfer modules in a system taken worst case read or write Example 1 A PLC 2 30 programmable controller is controlling 4 I O chassis in a remote configuration with 1 assigned rack number per chassis Figure A 1 An encoder module is located in each chassis Assume the 2 words are transferred in each read operation 20 words are transferred in each write operation and that the ladder diagram program contains 4K words There are no other block transfer modules in the system A 2 Appendix A Figure A 1
53. r of wires remains put them in parallel to reduce the voltage drop between the power supply and the encoder Figure 3 4 Do not source current such as from a power supply into the encoder input terminals of the module Doing so can damage input circuitry For the best system noise immunity we recommend use of a separate linear regulated power supply for powering the input circuitry and the encoder You can use this supply for more than one absolute encoder module or encoder but do not use it for other 5V loads such as relays Make sure the power supply has enough additional current capacity for the encoder Figure 3 4 Connecting Extra Pairs of Wires Between the Module and Encoder for Power Supply Connections 5V Encoder Supply Common a Terminal 21 of Left Wiring Arm e e d 5V supply mE O Terminal 21 of Right Wiring Arm 12835 Chapter 3 Configuring and Installing Your Module Output Power Supply To power the eight outputs Figure 3 5 connect at least one 5 to 24V DC supply to terminal 1 and terminal 6 or 7 of the right wiring arm You can connect another 5 to 24V DC power supply between terminals 9 and 14 or 15 of the right wiring arm if for example you need two different load supply voltages If you need only one supply voltage connect a wire between terminals 1 and 9 and connect another wire between terminal 6 or 7 and
54. rite 2 512 ms for channel 1 and 77 ms for channel 3 from Step 3 Read Write Time Program scan 2 Scanner scan encoder 50 2 512 module in 50 1024 channel 1 1074 ms 1 1 seconds Time Program scan 2 Scanner scan encoder 50 2 77 module in 204 ms channel 3 A 12 Application Considerations Appendix Application Considerations The absolute encoder module can control outputs within a one count resolution turn an output on at position 065 and off at position 066 if shaft speed does not exceed a certain limit This speed limit depends on the number of outputs and the number of counts on the encoder It can be found from S K N where S maximum shaft speed for one count resolution K a constant and N number of counts on the encoder The value of K depends on whether you want to express shaft speed in revolutions per second rps or revolutions per minute rpm If you control Then K for rps OR K for rpm 4 outputs 9009 540 540 2 outputs 14 084 845 070 For example if you control eight outputs with a 0 to 359 count encoder and the encoder shaft speed is given in revolutions per minute the equation is 300 000 S 360 833 rpm The maximum encoder shaft speed at which you can control eight outputs within a one count resolution is 833 rpm Let s consider two examples to show the importance of shaft speed number of outputs to be controlled and number of encoder count
55. s in obtaining optimum module operation In both examples we use a 0 to 359 count encoder all eight outputs are under control and the output is to turn on at position 000 and off at position 001 B 1 Appendix B ri Shaft Position Encoder LSB Bit 0 New Position Throughput Time Output Bit Na 000 In the first sample Figure B 1 we assume that the encoder shaft is turning close to the maximum allowable shaft sped according to the above equation The shaft is in each discrete position for only 220 us giving 360 increments or one revolution every 79 ms This is equal to about 758 rpm In the second example Figure B 2 we assume a more typical shaft speed of 60 rpm or one revolution per second The encoder spends about 2 8 ms in each discrete position Figure B 1 Encoder Operating Near Maximum Speed 758 RPM 001 002 lt 200s m gt B 2 13306 Appendix B Figure B 2 Encoder Operating at Typical Speed 60 RPM 4005 Shaft Position 000 001 002 Encoder LSB Bit 0 lt 28ms gt New Position Throughput Time Output Bit 13307 The first waveform of Figure B 1 and Figure B 2 represents the least significant bit LSB or bit 0 of a BCD or binary encoder The LSB changes with every change in encoder position one increme
56. same scan when you use the offset feature An example program enabling the instructions in separate scans follows WARNING When the block lengths of bidirectional block transfer instructions are set to unequal values do not enable the rung containing the alternate instruction until the done bit of the first transfer is set If you enable them in the same scan the number of words transferred may not be the number intended invalid data could be operated upon in subsequent scans output devices could be controlled by invalid data Unexpected and or hazardous machine operation could occur Damage to equipment and or injury could result Chapter 5 Offset Programming LADDER DIAGRAM DUMP 200 START 077 L L 1 L POWER UP BIT 06 OFF00 200 Cal es Na WRITE DATA VALID BIT 121 ae 00 PUSHBUTTON TO CHANGE PRESETS 122 200 077 e U 06 04 OFF00 22 122 022 Lag i BLOCK XFER READ EN 06 07 DATAADDR 0040 07 READ FILE MODULE ADDR 220 122 DONE DONE BLOCK LENGTH 02 _ py BIT BIT FILE 0200 0201 07 122 044 oe BUFFER FILE FILE TO FILE MOVE 0044 COUNTERADDR 0044 EN 07 15 POSITION 001 CEN FILE LENGTH 002 17 FILE A 0200 0201 0044 FILE R 0226 0227 RATEPERSCAN 002 DN 15 077 022 122 022 ESI l l BLOCKXFERREAD EN 00 07 06 DATA ADDR 0041 06 MODULEADDR 220 499 BLOCK LENGTH 22 py FILE 0202 0227
57. sis backplane and wiring arm before installing or removing the module Failure to remove power from the backplane or wiring arm could cause module damage degradation of performance or injury Failure to remove power from the backplane could cause injury and or equipment damage due to possible unexpected operation WARNING Install the module in the I O chassis so that both halves of the module are in the same I O group Failure to observe this rule will result in faulty module operation and or damage to the module circuitry with possible injury to personnel CAUTION Do not force the module into a backplane connector If you can t seat it with firm pressure check the alignment and keying You can damage the connector or the module if you force it into the connector 1 Remove power from the I O chassis before inserting or removing the module 2 Open the module locking latch on the I O chassis and insert the module into the slot keyed for it 3 Firmly press to seat the module into its backplane connector 4 Secure the module with the module locking latch 3 11 Chapter 3 Configuring and Installing Your Module Summary 3 12 This chapter told you how to select features and set configuration plugs on the absolute encoder module and described the power requirements keying wiring and installation of the module In the next chapter you will read about block transfer file parameters Chapter Objectives
58. t position If your Gray and E15 is in the encoder encoder has this position shows left a decreased count starting with 4 095 This configuration plug does not affect BCD or binary encoders Selecting State of Outputs Upon Loss of Input Power Use configuration plug El on the right board to choose the state of the outputs if the module loses input power The plug is factory set for the outputs to turn off if input power is lost up position If you want the outputs to remain in their state at loss of input power set the plug to the down position Except for downloading programs or commands and reporting status the module operates independent of the host processor In the event of a processor or I O communications fault the module either continues operation or its outputs turn off depending on how you set the last state switch of the chassis in which you place the module If you set the last state switch to turn outputs off the module s outputs are turned off If you set the last state switch to hold outputs in last state the module continues operating Plastic keying bands are shipped with each I O chassis These bands ensure that only a selected type of module can be placed in a particular Power Requirements Chapter 3 Configuring and Installing Your Module I O chassis module slot They also help to align the module with the backplane connector Each module is slotted at its rear edge The position of the key
59. t the chassis and the block transfer module s that it contains as often as it is listed The procedure for calculating block transfer timing for a PLC 3 processor is given here followed by an example calculation 1 Determine the number of active I O channels on the scanner and the number of I O channels with block transfer modules Show the number of block transfer modules in each I O chassis block transfer I O channels I O chassis entries in the rack list for each block transfer I O channel active I O channels per scanner A 9 Appendix A A 10 4 Determine the nominal block transfer time Compute the approximate scanner time for each block transfer channel Compute the encoder re write block transfer time Example Computation An example computation to determine the block transfer timing with a PLC 3 family processor follows The example is based on these facts user program contains 20K words 1 channel 1 contains five I O chassis with a total of seven block transfer modules including one encoder module channel 2 contains two I O chassis with no block transfer modules channel 3 contains two I O chassis with one encoder module channel 4 is made inactive through processor LIST Diagram the chassis connected in series to each channel up to four of your scanner module Then fill in the information called for below Example values have been added
60. the absolute encoder module Figure E 1 shows you how to connect a Bulletin 845A encoder 0 to 359 count 10 bit BCD single ended output encoder Figure E 2 shows you how to connect a Bulletin 845A encoder 0 to 255 count 8 bit Standard Gray single ended output encoder Figure E 3 shows you the connections for a Bulletin 845C encoder 0 to 359 count 10 bit BCD single ended output latching encoder 0 to 359 count 10 bit BCD Follow these guidelines Single ended Output f Make the wht orn wire pin V an open connection The encoder counts up in a counterclockwise direction if you make the wht yel wire pinQ an open connection or if you connect it to 5V if you connect it to ground the encoder counts up in a clockwise direction Signal common wht blk pin W and ground blk pin X are internally connected on the encoder Jumper the unused most significant bit input terminals E 1 Appendix E Figure E 1 Connection Diagram for Allen Bradley Encoder Bulletin 845A BCD Left TISSUE Right Wiring Wiring Arm Arm Pin R BRN DECADE 1 1 ees SI Pin K ORN DECADE 1 2 Q Pin E YEL DECADE 1 4 GJ Pin A GRN DECADE 1 8 S Pin B BLU DECADE 2 1 GJ Pin G VIO DECADE 2 2 GJ Pin C GRAY DECADE 2 4 SN Pin H WHT DECADE 2 8 Q Pin D WHT RED DECADE 3 1 Q Pin J WHT BRN DECADE 3 2 N Pin Z RED 5V dc
61. the format of one word the module continues to identify other non BCD words Word 2 indicates the current position of the encoder with the offset value in BCD Figure 5 2 Format of Block transfer read Data With Offset 17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00 Status of Outputs Th Ak hk hk Output 7 Code indicating which preset or offset word is in non BCD format Non BCD preset flag Output 3 Non BCD offset flag Output 2 Write data valid Output 1 Loss of input power Output 0 Word 2 Current Absolute Positiont Offset in BCD 10216 I 5 5 Chapter 5 Offset Programming Programming Considerations with Offset 5 6 The default block lengths 00 for block transfer instructions are 20 block transfer write words and two block transfer read words These are the block lengths that transfer to and from the absolute encoder regardless of whether you use the offset feature When you have an offset value and the module is controlling eight outputs for example the number of words you send to the module is 22 You must enter the numbers 22 and 2 for the block lengths of write and read data Do not enter the default block length in your instructions if you use the module s offset feature For PLC 2 family processors do not enable the read and write block transfers in the
62. tion Description Recommended Action ACTIVE FAULT Normal operation module should operate when the PC goes into the RUN mode and you send presets ACTIVE Module is held reset at power up probable Substitute adapter module power supply or malfunction in adapter module or processor processor module FAULT module ACTIVE Module has detected a hardware fault in its Return module for repair FAULT power up diagnostic routine ACTIVE Module is not receiving DC power from the Check chassis power supply ies FAULT chassis backplane Causes of Block transfer Errors OOOO Observe the block transfer rungs in your ladder diagram program You have a block transfer error when you observe one or both of the following The block transfer error bits are intensified PLC 3 processors The enable and done bits of block transfer instructions do not intensify or they remain intensified they should alternately turn on intensify and turn off Block transfer errors are caused if one or more of the following are incorrect The module s location rack group slot in the I O chassis must match the rack group and slot of block transfer instructions in the ladder program 6 1 Chapter 6 Troubleshooting Errors Indicated by Diagnostic Bits Summary 6 2 The block lengths of read and write block transfer instructions should be equal PLC 2 family processors or if they are different lengths do not enabl
63. trol Word for Outputs 0 and 1 16 ZT 15 gt 14 13 lt 12 gt 11 z 10 lt 07 OE 06 ZT 05 gt 04 03 lt 02 gt 01 00 lt Output enable bit set this bit if you want output 1 turned on when comparisons with presets 1A and 1B are true Zero transition bit set this bit when you want output 1 energized during a transition through position 000 Comparison bit for preset 1B Comparison bit for preset 1B Comparison bit for preset 1B Comparison bit for preset 1A Comparison bit for preset 1A Comparison bit for preset 1A Output enable bit set this bit if you want output 0 turned on when comparisons with preset 1A and 1B are true Zero transition bit set this bit when you want output 0 energized during a transition through position 000 Comparison bit for preset 0B Comparison bit for preset 0B Comparison bit for preset 0B Comparison bit for preset 0A Comparison bit for preset 0A Comparison bit for preset 0A D 1 Appendix D Preset Words a einen Preset value A for output 0 Preset value B for output 0 Preset value A for output 1 2 3 4 5 Preset value B for output 1 7 Preset value A for output 2 8 Preset value B for output 2 9 Preset value A for output 3 10 Preset value B for output 3 12 Preset value A for output 4 13 Preset value B for output 4 14 Preset value A for output 5 15 Preset value B for output 5 17 Preset value A for output 6 Preset
64. ule a 3 11 Module Processor Communication 4 1 Chapter Objectives 00 cece eee eee eee 41 Block Transfer 4 acids cos rc eoe dene aeu Comte teen 4 1 Block transfer write Data 2 0 cece eee 41 Write Data Throughput Time a 44 Block transfer read Data a 4 4 Programming Example nonan a 4 5 Programming Considerations a 4 7 im mg SUMMAT MERE ET etera iea C EE ETT LT Table of Contents Offset Feature 0c c cece eee eee eee eee Offset Feature 20 cee III Offset Words coded S KANA S ER CRPESEN ds pies cess Programming Considerations with Offset Troubleshooting leere Chapter Objectives 0 aa Causes of Block transfer Errors 0 0 0 aa Errors Indicated by Diagnostic Bits 000 SUMMANY Louis ed ooh eee eink urapa eee E eens Block transfer Timing 00 llli Block transfer Timing for PLC 2 Family Processors Block transfer Timing for PLC 3 Family Processors Application Considerations aa Application Considerations 0 aaa Block transfer Ladder Diagram Examples Bidirectional Block transfer for PLC 2 Family Processors Bidirectional Block transfer for PLC 3 Processors Read only Block transfer for PLC 2 Family Processors Bit and Word Descriptions of Block transf
65. will be performed correctly but the status of the outputs read by the PC may not correspond to the encoder position value This may not matter in your application if you do not use the read data in your PC application program However if this is not acceptable you may be able to trade resolution for speed Remember that the maximum shaft speed depends on the number of encoder positions A 0 to 4 095 count encoder has a lower maximum rpm rating than a O to 359 count encoder Similarly a 0 to 99 count encoder turns at an even higher rotational speed to control within a one count resolution You can also trade accuracy for speed Suppose your application can tolerate having an output come on anywhere between position 030 and 035 and go off between 045 and 050 The encoder shaft may be turning fast enough to go through several positions during the module comparison processing time The module reads position 028 during the first module scan and leaves the output off B 5 Appendix B B 6 During the next scan the module reads position 032 and turns the output on In this case you could program presets of 030 and 045 with the understanding that the change of output could occur a few increments after those positions Hardware RC filtering in the module input circuitry is designed to attenuate high frequency noise spikes that may pass through the opto isolators The maximum practical input frequency to the module input terminals

1771-6.5.32, Absolute Encoder Module User Manual

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