RLL Programming for Communications
Contents
1. sequenced by the two contacts C50 Truth Table C52 and C51 Two contacts provide four First RX WX 0 0 different binary states Second RX WX 6 5 e both off Third RX WX 0 1 e C50 on and C51 off Fourth RX WX 0 7 e C50 off and C51 on Fifth RX WX 1 0 0 pomon Sixth RX WX i 0 4 We only need to use three of the four Seventh RX WX 1 1 0 binary states circled since we only z have three RX WX instructions to EMM RANNA l i sequence First RX WX contacts They are normally closed in 7 17 1 K114 this rung to permit power flow to the first WX instruction Both bits are off a a corresponding to the first row of the LD truth table After the WX instruction is executed arin C50 is SET turned on which opens the contact in this rung and closes the C50 contact in the next rung WX VC100 C51 is RESET turned off which C50 leaves the C51 contact closed for the i aes CET next rung C51 RST 2 DC 9 Ew 9 SS 9E E 18 sO ro 2 Ethernet Communications Modules 3rd Edition Rev C 06 11 RLL Programming for Communications 4 19 armor birk i C50 is normally open and C51 is SP122 C51 C50 normally closed For this rung to be 7 17 ia executed the C50 bit must be on and the C51 bit must be off corresponding to the second row of the truth table LD C50 was turned on in the2. V377 TAO TA377 Counter Current Values V1000 V1377 CTAO CTA377 User Data Words V400 V777 V1400 V7377 V10000 V37777 None Input Points XO X1777 V40400 V40477 VX0 VX1760 Output Points YO Y1777 V40500 V40577 VYO VY1760 Control Relays CO C3777 V40600 V40777 VCO VC3760 Special Relays SPO SP137 SP320 SP717 V41200 V41205 V41215 V41234 VSPO VSP120 VSP320 VSP700 Timer Status Bits TO T377 V41100 V41117 VTO VT360 Counter Status Bits CTO CT377 V41140 V41157 VCTO VCT360 Stages SO S1777 V41000 V41077 VSO VS1760 Remote I O GX0 GX3777 GYO GY3777 V40000 V40177 V40200 V40377 VGXO0 VGX3760 VGY0 VGY3760 D4 430 CPU Data Registers Bit Memory Word Memory Alias Timer Current Values None VO V177 TAO TA177 Counter Current Values User Data Words None None V1000 V1177 V1400 V7377 CTAO CTA177 None Input Points Output Points XO X477 YO Y477 V40400 V40423 V40500 V40523 VXO VX460 VYO VY460 Control Relays Special Relays CO C737 SPO 137 SP320 SP617 V40600 V40635 V41200 V41205 V41215 V41230 VCO VC720 VSPO VSP120 VSP320 VSP600 Timer Status Bits Counter Status Bits Stages TO T177 CTO CT177 SO S577 V41100 V41107 V41140 V41147 V41000
3. in the V memory designation For example V40600 becomes 040600 Read instructions copy the data block from the responding PLC memory into the initiating PLC memory Write instructions copy the data block from the initiating PLC memory into the responding PLC memory Initiating PLC Ethernet Communications Modules 3rd Edition Rev C 06 11 K114 LD 4 words 8 bytes V40577 V40600 V40601 V40602 V40603 V40604 K114 K8 LDA 040600 RLL Programming for Communications 4 5 The Read RX instruction specifies the LD memory location to be read from the K114 responding PLC A block of data is read that begins at the LD specified memory location and extends the K8 number of bytes specified inthe second LD instruction ise In this example the eight byte block of data 040600 beginning at C100 and ending at C177 in the responding or slave PLC is read RX copied into the initiating PLC s memory C100 beginning at V40600 Initiating PLC Responding PLC V40577 V40603 V40600 V40604 V40601 V40605 V40602 V40606 V40603 V40607 V40604 V40610 Y Y byte byte Ga Y word 4 words 8 bytes Write WX The Write WX instruction specifies the LD Instruction memory location to be written to in the K114 responding PLC A b
4. S fe 5 D C62 is the interlocking contact It is turned on by the sequencing steps of _ rath the Shift Register in a preceding rung LD K2 LDA 040602 RX VC20 After this rung is executed the Shift Register shifts the high bit from C62 to C63 on the next CPU scan C63 resets the Shift Register to zeros the Store If Equal sets the C60 bit and the CPU executes the first RX WX instruction Ethernet Communications Modules 3rd Edition Rev C 06 11
5. V41027 VTO VT160 VCTO VCT160 VSO VS560 Remote I O GXO GX777 V40000 V40037 VGX0 VGX760 SUOI EOIUNWIWWOD JO Buiuuesbolq TIH Ethernet Communications Modules 3rd Edition Rev C 06 11 D4 440 CPU RLL Programming for Communications D4 440 CPU Data Registers Timer Current Values Bit Memory None Word Memory VO V377 TAO TA377 Counter Current Values None V1000 V1177 CTAO CTA177 User Data Words None V1400 V7377 V10000 V17777 None Input Points XO X477 V40400 V40423 VXO VX460 Output Points YO Y477 V40500 V40523 VYO VY460 Control Relays CO C1777 V40600 V40677 VCO VC1760 Special Relays SPO 137 SP320 SP717 V41200 V41205 V41215 V41234 VSPO VSP120 VSP320 VSP700 Timer Status Bits TO T377 V41100 V41117 VTO VT360 Counter Status Bits CTO CT177 V41140 V41147 VCTO VCT160 Stages SO S1777 V41000 V41077 VSO VS1760 D4 450 CPU Remote I O GXO GX1777 V40000 V40077 D4 450 CPU VGXO VGX1760 Data Registers Timer Current Values Bit Memory None Word Memory VO V377 TAO TA377 Counter Current Values None V1000 V1377 CTAO CTA377 User Data Words None V1400 V7377 V10000 V37777 None Input Points XO X1777 V40400 V40477 VX
6. into the accumulator and the first and second level of the accumulator stack The RX or WX instruction takes these parameters from the stack and the accumulator and prepares the data to be sent over the network If you need to know more about the function of the accumulator and the accumulator stack refer to the User Manual for your PLC Building the For network communications you build LD Read RX or the Read RX or Write WX instructions Adaa Write WX into a routine which requires the four Routine instructions you see to the right The function of each of these instructions is explained below or on the next page They Aaaa must be used in the sequence shown LDA O aaa RX or WX A aaa The first Load LD instruction accepts either a constant or a variable Use a K to designate the number as a constant Use a V if you are entering the address of a register The contents of that register perform the same function as the constant shown below For example you could use V2000 in place of K0114 Ifthe contents of V2000 is the number 114 the function would be the same Using a variable allows oxy changing parameters while the program is running It is recommended however to oF use a constant when possible S y 38 The First LD e i O Instruction LD a5 Upper Byte Lower Byte DENS Sz aa Z ee SE Initiating PLC J Responding
7. previous K2 rung C51 was turned off in the previous rung LD A After the WX instruction is executed C50 is RESET turned off which Wx opens the C50 contact in this rung and VCO closes it in the next rung C50 RST C51 is SET turned on which closes Tn the normally open C51 contact in the C51 next rung QET Third RX WX i SP122 Instruction In this last rung C50 is normally C51 C50 7 this rung to be executed the C50 bit closed and C51 is normally open For 7 K114 must be off and the C51 bitmustbeon LD corresponding to the third row of the ko truth table C51 was turned on in the previous rung LDA 040602 After the RX instruction is executed C50 is RESET which opens the C50 contact in this rung and allows it to pom close in preparation for repeating the first communication rung on the next c50 CPU scan page 4 18 RSD C51 RST Buiwwepoid TIH C51 is also RESET which allows the C51 contact to close in preparation for repeating the first communication rung on the next CPU scan page 4 18 s fe Q e 3 3 Cc 2 O fab ie J n Returning to the At the end of the third RX WX instruction we cycle back to the top row of the truth First RX WX table on page 4 18 Both C50 and C51 are off and the next CPU scan executes the Instruction first RX WX instruction Ethernet Communications Modules
8. 377 TAO TA377 Counter Current Values V1000 V1177 CTAO CTA177 User Data Words V400 V677 V1200 V7377 V10000 V17777 None Input Points See note 1 XO X777 V40400 V40437 VX0 VX760 Output Points See note 1 YO Y777 V40500 V40537 VYO VY760 SUOIJEOIUNWWWOD JO Bulwwesbolg TIH Control Relays CO C1777 V40600 V40677 VCO VC1760 Special Relays SPO SP777 V41200 V41237 VSPO VSP760 Timer Status Bits TO T377 V41100 V41117 VTO VT160 Counter Status Bits CTO CT177 V41140 V41147 VCTO VCT160 Stages SO S1777 V41000 V41077 VSO VS1760 Remote I O GX0 GX3777 GYO GY3777 V40000 V40177 V40200 V40377 VGX0 VGX3760 VGY0 VGY3760 1 The DLO6 systems are limited to 20 discrete inputs and 16 discrete outputs with the present available hardware but 512 point addresses exist Ethernet Communications Modules 3rd Edition Rev C 06 11 RLL Programming for Communications ep oc 9 EG 0 SE oe I e a ro D2 240 CPU D2 250 1 CPU NOTE The D2 230 CPU does not support the ECOM modules D2 240 CPU Data Types Timer Current Values Bit Memory None Word Memory VO V177 TAO TA177 Counter Current Values None V1000 V1177 CTAO CTA177 User Data Words None V2000 V377
9. 3rd Edition Rev C 06 11 4 20 RLL Programming for Communications Shift Register 2 oc 9 EG 0 SE oe I e a ro Store If Equal The Shift Register can be used for creating interlocks as an alternative to using control relays For a complete explanation of the function of the Shift Register see the User Manual for your PLC If you have more than a few RX WX instructions using control relays can become cumbersome The Shift Register allows a single contact to be used in each communication rung as an interlock place zeros When that condition is true the The data input to the Shift Register SP1 SR Cao SR is Special Relay SP1 SP1 is the always on bit Combined with a SP122 C77 normally closed contact it sends zeros j to the Shift Register data input The clock input to the Shift Register is er SP122 the communication busy bit Each time one of the RX WX instructions executes the Shift Register moves the set bit over one C63 is used in this example to reset the Shift Register to all zeros C77 C76 C75 C74 C73 C72 C71 C70 C67 C66 C65 C64 C63 C62 C61 C60 Shift Register after first scan C77 C76 C75 C74 C73 C72 C71 C70 C67 C66 C65 C64 C63 C62 C61 C60 Shift Register after second scan C77
10. 7 V4000 V4377 None Input Points XO X477 V40400 V40423 VXO VX460 Output Points YO Y477 V40500 V40523 VYO VY460 Control Relays CO C377 V40600 V40617 VCO VC360 Special Relays SPO SP137 SP540 SP617 V41200 V41205 V41226 V41230 VSPO VSP120 VSP540 VSP600 Timer Status Bits TO T177 V41100 V41107 VTO VT160 Counter Status Bits CTO CT177 V41040 V41147 VCTO VCT160 Stages Data Types Timer Current Values Counter Current Values User Data Words Input Points SO S777 V41000 V41037 D2 250 1 CPU Bit Memory None None None XO X777 Word Memory VO V377 V1000 V1377 V1400 V7377 V10000 V17777 V40400 V40437 VSO VS760 Alias TAO TA377 CTAO CTA377 None VX0 VX760 Output Points Control Relays YO Y777 CO C1777 V40500 V40537 V40600 V40677 VYO VY760 VCO VC1760 Special Relays Timer Status Bits SPO SP777 TO T377 V41200 V41237 V41100 V41117 VSPO VSP760 VTO VT360 Counter Status Bits Stages CTO CT177 SO S1777 Ethernet Communications Modules 3rd Edition Rev C 06 11 V41140 V41147 V41000 V41077 VCTO VCT160 VSO VS1760 D2 260 CPU D4 430 CPU RLL Programming for Communications D2 260 CPU Data Registers Timer Current Values Bit Memory Word Memory VO
11. C76 C75 C74 C73 C72 C71 C70 C67 C66 C65 C64 C63 C62 C61 C60 Shift Register after first RX WX C77 C76 C75 C74 C73 C72 C71 C70 C67 C66 C65 C64 C63 C62 C61 C60 Shift Register after second RX WX C77 C76 C75 C74 C73 C72 C71 C70 C67 C66 C65 C64 C63 C62 C61 C60 Shift Register after third RX WX C77 C76 C75 C74 C73 C72 C71 C70 C67 C66 C65 C64 C63 C62 C61 C60 Shift Register after third RX WX plus one scan The Store If Equal instruction detects V40603 KO c60 when the Shift Register is reset to SET C60 bit is SET by this rung The C60 bit becomes the high bit shifted by the Shift Register until each RX WX instruction is executed in turn Ethernet Communications Modules 3rd Edition Rev C 06 11 RLL Programming for Communications 4 21 First RX WX Instruction C60 is the interlocking contact It is 5P122 C60 turned on by the Store If Equal rung LA K114 preceding this one LD K2 LDA 040600 WX VC100 Second RX WX Instruction C61 is the interlocking contact It is 5P122 C61 t LD urned on by the sequencing steps of 17 K109 the Shift Register in a preceding rung LD K2 LDA 040601 WX VCO Third RX WX Instruction SP122 C62 Buiwwepoid TIH Z ej Q fe 3 Z gt O
12. CPU Base Slot 1 Slot2 Slot3 Slot4 Slot5 Slot6 Slot7 Communication busy SP122 SP124 SP126 SP130 SP132 SP134 SP136 Communication error SP123 SP135 SP137 D2 240 D2 250 1 D2 260 D4 430 and D4 440 Special Purpose Communication Relays CPU Base SlotO Slot1 Slot2 Slot3 Slot4 Slot5 Slot6 Communication busy SP120 SP122 SP124 SP126 SP130 SP132 SP134 Communication error SP121 SP123 SP125 SP127 SP131 SP133 SP135 DL405 Slot D4 450 Special Purpose Communication Relays SlotO Slot1 Slot2 Slot3 Slot4 Slot5 Communication busy Communication error Expansion Base 1 Communication busy Communication error 2 oc 9 EG 0 5 SE oe I e ae xo Expansion Base 2 Communication busy Communication error Expansion Base 3 Communication busy Communication error Ethernet Communications Modules 3rd Edition Rev C 06 11 RLL Programming for Communications 4 13 Program with One Read Instruction The Ladder View screen below is the program development screen in DirectSOFT Programming Software This four rung program is explained in detail on page 4 14 This is a complete program although its fun
13. O VX1760 Output Points YO Y1777 V40500 V40577 VYO VY1760 Control Relays CO C3777 V40600 V40777 VCO VC3760 Special Relays SPO SP137 SP320 SP717 V41200 V41205 V41215 V41234 VSPO VSP120 VSP320 VSP700 Timer Status Bits TO T377 V41100 V41117 VTO VT360 Counter Status Bits CTO CT377 V41140 V41157 VCTO VCT360 Stages SO 1777 V41000 V41077 VSO VS1760 2 oc 9 EG Eo 5 2E E I e ale ro 2 Remote I O GX0 GX3777 GYO GY3777 Ethernet Communications Modules 3rd Edition Rev C 06 11 V40000 V40177 V40200 V40377 VGXO VGX3760 VGY0 VGY3760 RLL Programming for Communications 4 11 Special Relays for Communications The DirectLOGIC PLCs provide internal contacts bits for monitoring the status of communications The internal contacts are called Special Relays there are other Special Relays used for other purposes There are two Special Relays for each slot in the base that will accept the ECOM module The two relays perform the following functions e Communication Busy This bit is on when the communication module is busy transmitting or receiving You must use this bit or relay contact to prevent overwriting your Read or Write RX WX instructions Communication Error This bit is on when an error occurred in the last RX or WX communication This error automaticall
14. PLC ae Master KO 1 1 4 Slave Base Number ECOM Slot Number ECOM Module ID CPU Base 0 Initiating PLC Responding PLC Expansion Base 1 or g See page 2 7 and 2 8 about See page 2 3 and 3 8 about See page 2 7 and 2 9 about us slot numbers setting the Module ID ing ECOMs in local expansion or in remote I O bases Ethernet Communications Modules 3rd Edition Rev C 06 11 4 4 RLL Programming for Communications ep oc ae EG 0 SE oe I e a ro The Second LD Instruction The LDA Instruction The second Load LD instruction determines the length of the data block to be transmitted during the Read or Write communication This instruction will also accept two data types Use a K to designate the number as aconstant Usea V if you are entering the address of a register For Word Memory data you must use a multiple of two bytes between 2 and 128 For Bit Memory data you can use any multiple of one byte between 1 and 128 For more information about addressing Word and Bit Memory see page 4 6 PLC Memory The Load Address LDA instruction specifies the V memory address of the beginning memory register in the initiating or master PLC The data block to be transmitted will begin at this address and extend the number of bytes specified in the preceding LD instruction The leading O indicates this is an octal number Simply substitute the letter O for the V
15. RLL Programming for Communications In This Chapter PLC to PLC Communications How RLL is Used for Communications Network Instructions Addressing the Different Memory Types Special Relays for Communications Example Program with One Read Instruction Example Program with One Write Instruction Integrating Multiple Read and Write Instructions 4 2 RLL Programming for Communications rp Oc 9 Ew 9 S5 SE oe 18 JO ro 2 PLC to PLC Communications This chapter steps you through the development of a Relay Ladder Logic RLL program to enable one PLC to communicate with another PLC For the experienced programmer of DirectLOGIC PLCs the communication programs presented in this chapter will be simple to follow If you have never programmed a DirectLOGIC PLC you may want to refer to the DirectSOFT Programming Software User Manual and the User Manual for your PLC for additional information NOTE The programs described in this chapter are not used for communication between a PC and a PLC For PC to PLC communications please see the product documentation for the PC software you are using If you are using our DSData Server software the manual you will need is the KEPDirect for PLCs User Manual How RLL is Used for Communications DirectSOFT Programming Software provides Read and Write instructions RX WX for PLC to PLC communication over a network The Read and Write instr
16. Read and Write Instructions Multiple Read and Write instructions require interlocks for sequencing because only one RX WX instruction can be processed per CPU scan Using interlocks one RX WX instruction is processed in each scan until all RX WX instructions have been executed After the last instruction the sequence then begins again at the first RX WX instruction Without interlocks the RX WX instructions would be executed in an unpredictable order and some might be executed many times before others are executed once The interlocks serve to open disconnect the ladder circuits for all Read and Write instructions except the one that should be processed on the current CPU scan We show two methods of creating the interlocks necessary for sequencing multiple Read and Write instructions e Sequenced Internal Control Relays e Shift Register We will step you through the development of the interlocks using both methods The two examples shown perform the same function Only the interlocks are different NOTE To fully understand the material in this section you will first need to understand the Example Programs on pages 4 13 and 4 15 as well as the material in the Network Instructions section beginning on page 4 3 The following program segment sequences through three RX WxX instructions two Write instructions and one Read instruction You can develop your own program incorporating either of the two interlocking cont
17. ction is very limited There is also a two rung program that runs in the responding PLC and itis also explained on page 4 14 Program for the inix Initiating PLC LDA 040600 RK VC100 Program for the Ej Ladder View HEL c100 A Responding PLC i a FEE Z END When the toggle switch input to the responding PLC is turned on transitions from 0 to 1 the CO bit in the initiating PLC transitions from O to 1 The program in the initiating PLC causes YO to turn on in response to the CO bit Module ID 3 site Module ID 14 I mk ej Q fe Z gt O S fe 5 D Bulwwesbolg TIH Responding PLC Hub slave Initiating PLC master For the purpose of these example programs both the initiating PLC and the responding PLC must be in RUN Mode Ethernet Communications Modules 3rd Edition Rev C 06 11 4 14 RLL Programming for Communications 2 DC 9 Ew 9 SS 9E E 18 sO ro 2 Rung 1 Rung 2 Rung 3 Rung 4 Program for the Responding PLC In our example the normally open contact labeled CO is an internal control relay When CO is on discrete output YO is energized The second rung uses a Special Relay to identify a communication error In the example SP123 is on if a communication error is present for slot one Use different Special Relays if your ECOM modul
18. e example SP123 is on if there is a communication error present in slot one Use different Special Relays if your ECOM module is in a different slot see page 4 11 and 4 12 We use SP123 to turn on an indicator light connected to a discrete output The Special Relay labeled SP122 is on when slot 1 is busy transmitting or receiving The Write instruction may take longer than one PLC scan to complete Use this Special Relay to prevent overwriting the previous Write instruction with each PLC scan Eppes Byie Lower Byte Initiating PLC Responding PLC Master KO 114 Slave Base Number y ECOM Slot Number ECOM Module ID BCD XO Co OUT SP123 Y1 SET SP122 LD K0114 LD K2 LDA 040600 Number of bytes to be transferred Max 128 bytes Beginning address in the initiating PLC expressed as an octal number Beginning address in the responding PLC All DirectLOGIC PLCs use an END statement to identify the final rung of the main body of the program This two rung program resides in the responding PLC s CPU Its function is simply to take the C100 contact and convert it to a real output YO Ethernet Communications Modules 3rd Edition Rev C 06 11 WX VC100 CEND OUT CEND RLL Programming for Communications 4 17 Integrating Multiple
19. e is ina different slot see page 4 11 and 4 12 We use SP123 to turn on an indicator light connected to a discrete output The Special Relay labeled SP122 is on when slot 1 is busy transmitting or receiving The Read instruction may take longer than one PLC scan to complete Use this Special Relay to prevent overwriting the previous Read instruction with each PLC scan Upper Byte Lower Byte J Initiating PLC Responding PLC Master Ko lt Ta Slave Base Number ECOM Slot Number ECOM Module ID BCD Number of bytes to be transferred Max 128 bytes Beginning address in the initiating PLC expressed as an octal number Beginning address in the responding PLC All DirectLOGIC PLCs use an END statement to identify the final rung of the main body of the program This two rung program resides in the responding PLC s CPU Its function is simply to use the XO contact to turn on the internal control relay C100 Co YO E OUT SP123 Y1 SET SP122 LD K0114 LD K2 LDA 040600 RX VC100 END XO C100 OUT CEND Ethernet Communications Modules 3rd Edition Rev C 06 11 RLL Programming for Communications 4 15 Example Program with One Write Instruction The Ladder View screen below is the program development screen in DirectSOFT Programming Software This four r
20. lock of data is written that begins at the LD specified memory location and extends the K8 number of bytes specified in the second LD instruction SD LDA OF In the example the 8 byte block of data 040600 Ov beginning at V40600 and ending at V40603 33 in the initiating or master PLC is written Wx ES copied into the responding PLC s memory C100 53 beginning at C100 and ending at C177 23 Sa Initiating PLC Responding PLC V40577 V40603 V40600 V40604 V40601 V40605 V40602 V40606 V40603 V40607 V40604 V40610 J CA Y y byte byte Ce J Vv word 4 words 8 bytes Ethernet Communications Modules 3rd Edition Rev C 06 11 4 6 RLL Programming for Communications Addressing the Different Memory Types Some data types are inherently 16 bits long for example timer and counter current values Other data types are 1 bit long for example discrete inputs and outputs Word length and bit length data are mapped into Word Memory also known as V memory which allows you to address any of the different memory types as 16 bit words Bit Memory Bit memory can be addressed in Read and Write instructions by the name of the first bit of any byte If your second LD instruction contains the constant K8 eight bytes will be transmitted If you use CO in your RX or WX instruction you will transmit the eight bytes from CO through C77 Word Memory In the example below V40600 is the V memory designation for the sixteen bits from and Aliases CO th
21. on Rev C 06 11 DirectSOFT is Flexible DLO5 CPU DLO6 CPU RLL Programming for Communications 4 7 You can address the different data types by any available convention shown in the tables that follow The largest block of data that can be sent ina single Read or Write operation is 128 bytes The smallest block of data is one byte for Bit Memory types and two bytes or one word for Word Memory types The octal numbering system is used for all addresses in these tables DLO5 CPU Data Types Timer Current Values Bit Memory None Word Memory VO V177 TAO TA177 Counter Current Values None V1000 V1177 CTAO CTA177 User Data Words None V1200 V7377 None Input Points See note 1 X0 X377 V40400 V40417 VX0 VX360 Output Points See note 1 YO Y377 V40500 V40517 VYO VY360 Control Relays CO C777 V40600 V40677 VCO VC760 Special Relays SPO SP777 V41200 V41237 VSPO VSP760 Timer Status Bits TO T177 V41100 V41107 VTO VT160 Counter Status Bits CTO CT177 V41140 V41147 VCTO VCT160 Stages SO S377 V41000 V41017 VSO VS360 1 The DLO5 systems are limited to 8 discrete inputs and 6 discrete outputs with the present available hardware but 256 point addresses exist DLO6 CPU Data Types Timer Current Values Bit Memory Word Memory VO V
22. rol strategies and expanding the number of interlocks to accommodate the number of RX WxX instructions in your program Interlocking It is easy to see the function of the interlocking relays if we construct a truth table first i Relays lt D f Across the top of the truth table we n Re OF show internal control relays that we Truth Table C52 051 C50 37 are considering using for our dn 38 sequencing strategy We have used First RX WX 0 0 0 59 C50 through C52 for our chart but Second RX WX SE any contacts that are not used for os other purposes in your program will hird RX WX Ze work just as well Fourth RX WX Fifth RX WX Down the left side of the chart we list the number of RX WX instructions we _ Sixth RX WX may want to use in our RLL program Seventh RX WX O O O O O O O O The three contacts in this truth table Eighth RX WX will accommodate as many as eight Read or Write instructions Our program only has three RX WX instructions so we only need to use two contacts see why on page 4 18 We will use C50 and C51 One additional contact C53 would give us 32 combinations since the number of combinations expands as the power of 2 Ethernet Communications Modules 3rd Edition Rev C 06 11 4 18 RLL Programming for Communications Our three RX WX instructions can be
23. rough C17 Aliases are a convenient substitute for V memory designations and can be used interchangeably in Read and Write instructions VCO is the alias for V40600 Either nomenclature addresses the same 16 bits The alias is simply the name ofthe first bit in a group of sixteen bits with V added as a prefix For example VCO represents the 16 bits beginning with CO Word Memory Bit Memory and Aliases all use the octal numbering system Word Memory Address V40600 VCO Alias C17 C16 C15 C14 C13 C12 C11 C10 C7 C6 C5 C4 C3 C2 C1 CO V40601 VC20 C37 cs C35 C34 C33 C32 C31 C30 C27 C26 C25 C24 C23 C22 C21 C20 V40602 VC40 C57 ose C55 C54 C53 C52 C51 C50 C47 C46 C45 C44 C43 C42 C41 C40 wn 25 V40603 VC60 c77 076 C75 C74 C73 C72 C71 C70 C67 C66 C65 C64 C63 C62 C61 C60 EG E E De The following Write routines are all equivalent DirectSOFT gives you the flexibility ae to identify the responding PLC s memory area in three different ways as shown 48 below rs LD LD LD K114 K114 K114 LD LD LD K8 K8 K8 LDA LDA LDA 040600 040600 040600 WX WX WX C c10 gt VC100 V40605 Ethernet Communications Modules 3rd Editi
24. uctions are part of the ladder logic program running in the CPU of the initiating or master PLC These instructions tell the initiating CPU to send a message over the Ethernet network to a responding or slave PLC The ECOM module is the connecting point to the network for each PLC The initiating PLC s Read or Write communication finds its destination by the Module ID of the responding PLC s ECOM module See Chapter 2 and 3 for information about assigning Module IDs Module ID 14 I Module ID 3 A y Initiating PLC pa Hub Responding PLC Module ID 9 Module ID 20 In the figure above the initiating PLC sends a Read or Write message to the responding PLC s ECOM module which is designated as Module ID 14 The responding PLC processes the message Any one of the PLCs could initiate communication with any one of the others Ethernet Communications Modules 3rd Edition Rev C 06 11 RLL Programming for Communications 4 3 Network Instructions Read RX and The Read RX and Write WX instructions are used by the initiating PLC to Reada Write WX block of data from another PLC or Write a block of data to another PLC To perform Instructions their functions the RX and WX boxes must be preceded in the ladder logic program by two Load instructions and one Load Address instruction The Load and Load Address instructions load communication parameters
25. ung program is explained in detail on page 4 16 This is a complete program although its function is very limited There is also a two rung program that runs in the responding PLC It is also explained on page 4 16 Program for the tedderview io Initiating PLC LD K2 LDA 040600 C100 Program for the Hill Ladder View Responding PLC a our 2 When the toggle switch input to the initiating PLC is turned on transitions from 0 to 1 the C100 bit in the responding PLC also transitions from 0 to 1 The program in the responding PLC causes YO to turn on in response to the C100 bit ej im Q fe Z gt O S fe 5 D Bulwwesbolg TIH Lee Module ID 14 Module ID 3 ie Responding PLC Hub slave Initiating PLC master For the purpose of these example programs both the initiating PLC and the responding PLC must be in RUN Mode Ethernet Communications Modules 3rd Edition Rev C 06 11 2 oc 9 EG 0 5 SE oe I e ae xo 4 16 RLL Programming for Communications Rung 1 Rung 2 Rung 3 Rung 4 Program for the Responding PLC In our example the normally open contact labeled XO is a toggle switch input to a discrete input module When XO is on Control Relay CO is energized The second rung uses a Special Relay to identify a communication error In th
26. y clears the bit resets to zero when another RX or WX instruction executes For example Special Relays SP124 and SP125 correspond to an ECOM module eee in slot 3 of the PLC base S araa aa a SET The Special Relay SP125 is used in the example to energize the output Y50 indicating a communication error has LD occurred This Special Relay must 3 K204 appear earlier in the program than your D ARNA A RX or WX instruction because it is turned off reset to zero when a subsequent See oa i Read or Write instruction is executed i SEERE EN The Special Relay SP124 indicates the es LDA ECOM is busy When SP124 is on the oS oi normally closed contact opens to prevent E executing another RX or WX instruction i RX until the last one is completed The A appropriate busy bit must be used as a NC contact on every RX WX instruction rung in the program Buiwwepoid TIH DLO5 Special Purpose Commu nication Relays CPU Base Option Slot Communication busy SP120 Z ej Q Q Z gt O S fe 5 D Communication error SP121 DLO6 Special Purpose Communication Relays CPU Base Slot1 Slot2 Slot3 Slot 4 Communication busy SP120 SP122 SP124 SP126 Communication error SP121 SP123 SP125 SP127 Ethernet Communications Modules 3rd Edition Rev C 06 11 RLL Programming for Communications DL240 DL250 1 and DL260 Special Purpose Communication Relays
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