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1. J IOExpansion v Extract of Epp Address Register is written at the end of the Epp Address Strobe because Epp Write control line is low indicating intent to write Adept 2 0 or higher running on your PC control the Cypress interface chip and causes communication between the Adept GUI on your PV display and the Cypress chip The Cypress chip is the Epp master which drives the three control lines EppAstb Epp Address Strobe active low ending edge is posedge EppDstb Epp Data Strobe active low ending edge is posedge EppWr Epp Write Control active low low means intent to write high means intent to read The EppDB is the Epp 8 bit data bus During an active address or data strobe Epp master drives data if write is true EppWr 0 else slave drives data if read is true EppWr 1 Active low WAIT active high GOT acts like a hand shake signal between the two parties Address Read Cycle is not implemented in Adept Virtual I O protocol EE254L_divider fm 7 19 14 12 15 C 2014 Gandhi Puvvada 12 Adept Application User s Manual pdf Config Test Register I O File l O I O Ex Settings To FPGA From FPGA Light Bar OxfTffttTT 00902 1990000110000 DODODODONIODOOOO0RRRNANNN Please refer to the Adept User s manual on crs Les your PC Start gt All Programs gt Digilent gt i piii E Adept gt Adept Application User s Man ss seat Lodf Extract of it is sh the sid PA oe ee eee eee eee ual pdf Extract of it is
2. Dstb is active and address if Astb is active Since these strobes carry timing information also we do not need the strobes to carry timing information Instead in Epp we have WR line which can be viewed as indicating the direction of transfer WR 0 means write and WR 1 means read In microprocessor memory interface we have a READY line not shown on the side which allows a slow memory to request for more time to respond Here we have wait to implement a 4 way handshake protocol a Take it 2 Got it 3 I see you got it 4 I see that you saw that you got it How does the Epp protocol provide for multiple data transfers in the absence of an address bus The Epp master can convey an address first using DB 7 0 and Astb and then later data using DB 7 0 and Dstb for that addressed location Oh it means we can at most exchange 256 bytes because using 8 bit address you can only generate 2 256 addresses No it is not like that The Epp master and the Epp slave can have a common understanding that the master always sends address in two parts high part followed by low part before data is transmitted This increases the number of bytes that can be transferred to 64KB 21 65536 64K used in PC XT EppAstb EppDstb EppWr 8 EppDB Epp Wait Epp Master Epp Slave Data Write or Of HHO EPP Address register always posedge EppAsthb begin if Eppwr regEppAdr lt EppDB
3. hot compact sequential gray johnson speed1 user The default is auto EE254L_divider fm 7 19 14 5 15 C 2014 Gandhi Puvvada Read the code ee254_debounce_DPB_SCEN_CCEN_MCEN v and complete the state diagram on the next page Simulate it using ee254_debounce_DPB_SCEN_CCEN_MCEN_tb v for 9 us ee201 debouncer N dc 4 ee201 debouncer 1 CLKE Clk th RESET Reset th PB PR tb DFB DPE tbh SCEN SCEN tb MCEN MCEN tb CCEN CCEN tb Notice that the testbench has instantiated the UUT with N_dc of 4 in the generic map 2 booa poo 100000 Pa ta fio Tt tiboooo ft ano Y yioo yioo f yi0o Y yioo fioo Y yioo V fioo 10110 YW A WH A LAN Oe ree WH iooe oor foor T foc Ty C TG CCE CCE JMCEN A simple rather construed example of the SCEN pulse of debouncer is as follows Suppose we are run ning short of the buttons on the board and we wish to use a single button BtnL both as a START button and an ACK button Then DPB pulse does not help as our divider is running at full speed 1LOOMHz and one operation of the BtnL say 0 2 sec will be considered as several hundred thousands of these START and ACK operations So when you let the BtnL go you can not tell whether the state machine is waiting in the Initial state or Done state But with SCEN only one clock wide pulse per operation is applied to the cir cuitry ee254 divider _with debounce Go
4. shown on the side noooooo00o eee ee F O rm 13 ee254_divider_with_VIO_multi_step VIO Virtual I O il satio i e You can control the system board using the expanded virtual I O controls on the I O Ex tab Here we are interfacing to the virtual I O in The expanded I O controls include 16 switches 16 Adept 2 0 The file IOExpansion vhd pro buttons 8 LEDs 24 individual light bars and the ability to send and receive a 32 bit value 10 Adept ts to the I O Ex configuration wh the Start VO button A special vided by Digilent implements the Epp slave _Fanshrarlaregeter s checked is very that te VO Ex design i active in the FPGA Wt vali the side address and data registers in FPGA We I O Ex status light turns green If it isn t the light turns yellow but the I O registers are still polled translated the same to Verilog The file is De semen eee realy tine Sol ban ete called IOExpansion v Note that now the Switches are flipped and buttons pressed by clicking on the graphics UCF file needs to have pins associated with Epp to talk to the Cypress USB interface chip The next two pages show the utilization of I O resources on the Nexys 3 board and in the Virtual I O GUI One important difference between the debouncer user earlier ee254_debounce_DPB_SCEN_CCEN_MCEN v and the debouncer used in this part ee254_debounce_DPB_SCEN_CCEN_MCEN_r1 v 1s that here Gn _r1 version we have increased the tim
5. through the files and download the provided bit file and test START ACK QUOTIENT ar ae a ee DIVDND DIVISOR REMINDER e a 3 Qi INITIAL 3 Qc COMPUTE 1 Qd DONE_S eo BtnL an Note that unlike in the earlier design ee254_ divider_simple we run the core divider in this design at the a 7 5 full speed of 100Mhz m A P O straw ax DIVIDEND DIVISOR Questions on the debouncer and the divider with debouncer 1 Briefly explain why the N_dc parameter was changed to 4 during simulation from the actual value of 25 for synthesis and implementation Use words such as inefficient wasteful readability of waveform etc 2 When you simulate zoom into the area of above waveform extract and arrive at your answer for the above question in the waveform extract why do we see 8 more pulses on MCEN after already seeing two pulses 3 Did we use the DPB Debounced Push Button pulse or SCEN Single Clock enable pulse to act as the Start signal and the Acknowledge signal Could we have used anyone of them EE254L_divider fm 7 19 14 6 15 C 2014 Gandhi Puvvada Complete the Debouncing State Machine with the added state MCEN_cont Complete the missing state transition conditions and also any RTL in the state MCEN_Cont CCEN_St I lt 1 DPB 1 CCEN 1 MC stands for MCEN count After certain count of MCN control is transferred to MCEN_ Con
6. EE254L Divider design Objective To introduce to students RTL coding style for state machine and datapath coding Testbench with a task debouncing mechanical Push Buttons and generating DPB SCEN MCEN CCEN Single stepping and Multi stepping using the push button debounce unit Introduce Epp protocol Exploit the I O resources in Adept 2 0 I O Expansion References for the TAs not for students 1 Nexys 3 board reference manual Nexys3_rm pdf and schematic http digilentinc com Products Detail cfm NavPath 2 400 897 amp Prod NEXYS3 http digilentinc com Data Products NEX YS3 Nexys3_rm pdf http digilentinc com Data Products NEX YS3 NEX YS3_sch pdf 2 Epp protocol First 4 pages of the Digilent Parallel Interface Model Reference Manual http www digilentinc com Data Products ADEPT DpimRef 20programmers 20manual pdf Files provided A zip file is provided containing source files for four sample designs in four folders Please read the notes at the top of each file to get to know important aspects of the design to note l ee254 divider _simple 2 ee254 divider with debounce 3 ee254 divider with single step 4 ee254 divider_with_VIO_multi_step A short description of each of the above 3 designs follows 3 ee254_ divider_simple Points to note The datapath elements shall be inferred by the syn thesis tool So we do not code OFL explicitly See the diagram on the next page The datapa
7. divide F by 0 How about 0 divided by 0 B If you improve the divider design to move from compute state to done state if X is equal or less than Y instead of the current X less than Y will the above behavior change Does your answer to Q 1 above change C Why does the behavior of the next design ee254_divider_with_debounce appear to be quite different from this design for division by zero Is it just appearance only or is it really different Note Look at the rate at which sysclk runs in both designs EE254L_divider fm 7 19 14 2 15 C 2014 Gandhi Puvvada 4 Bouncing of mechanical Switches and Push Buttons sy ne ea bance 3 3V VCC 5V VCC 5V ee 7 BtnL z l i l A Buttons BTNR sa 10KQ OPEN ie eae a A8 OPEN Low when aa ye High when SW is open c3 SW is ope SW SW B8 10KQ tnC I C for Center Works for TTL and CMOS logics Works for CMOS but not TTL logic Buttons on Nexys 3 When pressed they produce high PB 0 084s ae DPB SCEN 5 Debouncing State Machines Debouncing State Machine To start with just produce DPB and SCEN PB T 0 084 SCEN_St I lt 0 DPB 1 SCEN 1 PB T 0 084 PB T 0 084 PB Push Button PB 1 gt Push Button pressed WQ Wait for a Quarter Second actually 0 084ms SCEN Single Clock Enable enable the RTL transfer operation and or state transfer operation for one clock of the 100 MHz system clock CCR Clear Counter WFECR Wait For Complete R
8. dot matrix printer in 1980 s Micro AB USB fg USB E http en wikipedia org wiki IEEE_1284 It is a very simple Connector ee Controller gt PP interface and easy to use though obsolete Since USB inter CY7C68013A JTAG Port face is a fairly complex interface and since current PCs do Nexys 3 Board not support Epp interface Cypress http www cypress com offer USB interface chips which convert the USB interface to simple interfaces such as Epp Since Epp is a very simple interface Digilent chose to use a Cypress interface chip CY7C68013A on their Nexys 3 boards to convert communi cations from and to a PC on USB to Epp for us to deal with on the FPGA Digilent has also provided the Adept software to cnn en run on the PC and communicate with the Cypress chip on ins Bim USB They have also provided IOExpansion vhd which we _Senis_Memon Test Register Ho File yo we Ex Setings translated to Verilog for EE254L as IOExpansion v for gooooooooonooononononann instantiation in FPGA side designer s top file The UCF file Format Hexadecmal v e0 606006 for such project should include the pins associated with the Epp interface On the Adept GUI the Register I O the File I epee eee og 2 O and the I O Ex Here in this lab we explore the I O Ex tab oe oe oe a ro which we refer to as Virtual I O We call it Virtual I O as it adds several addition Switches Push Buttons LEDs on the GUI to the limited n
9. e gap between consecutive MCEN pulses to 1 342 sec Hence instanti ations of the debouncer uses here an N_dc parameter of 28 ee254 debouncer N_dc 28 ee254 debouncer 2 Task to be performed Download the zip file provided to you into your C xilinx_projects directory and extract files to form C Xilinx oe ee divider_verilog directory with 4 sub folders ee254 divider_simple ee254 divider with debounce ee254 divider_with_single step 4 ee254 divider_with_VIO_multi_step All the four folders have verilog source files ucf source file a bit file with Tas_prefix of the completed design ue ae After reading the code you can download the bit file to the Nexys 3 board and operate the divider The bit files provided to you have a TAs_ prefix so that you do not overwrite when you compile the sample designs to get practice in forming a xilinx project and implementing the same When you are done you will submit a report to your TA with your answers to questions posted under first three designs No questions are posted for this last design 14 Celebrate your success Don t forget this step EE254L_divider fm 7 19 14 13 15 C 2014 Gandhi Puvvada Adept Virtual I O resource utilization for this part of the lab unused resources are crossed out ee254_divider_with_VIO_multi_step Multiplexing the two displays on the four 7 seg displays using Btn ct ob et i Pe a L when btnR is not pressed o through the file
10. elease DPB 1 in all states except for INI and WQ states SCEN 1 in SCEN_St only Hence SCEN is a single clock wide pulse EE254L_divider fm 7 19 14 3 15 C 2014 Gandhi Puvvada Debouncing State Machine Now produce MCEN and CCEN besides DPB and SCEN PB T 0 084 SCEN_St PB T 0 084 PB T 0 084 PE gaa 1 PB CCEN St MCEN St 1 an PB T 0 168 I lt I 1 PB T 0 084 DPB I DPB 1 MCEN 1 CCEN 1 CCEN 1 PB T 0 084 PB T 0 168 MCEN Multiple Clock Enable of course with 0 084 sec gap CCEN Continuous Clock Enable with no gap MCEN is active in SCEN_ St and MCEN St CCEN is active in SCEN_St MCEN_ St and CCEN_St states 6 How to produce glitch free outputs from a state machine Earlier in class we showed how easily glitches are produced by a combinational logic such as a mux or an equality checker If we can avoid the OFL Output Function Logic in a Moore kind of state machine by cleverly coding symbolic states using output coding then the output control signals come out of state flip flops and they will be glitch free Original State Machine with OFL Output coded State Machine with no OFL EE254L_divider fm 7 19 14 4 15 C 2014 Gandhi Puvvada 7 ee254 divider_with debounce Let us go through the debouncer design ee254_debounce_DPB_SCEN_CCEN_MCEN v It debounces a given push button and produces 4 outputs DPB SCEN CCEN MCEN Output coding for the states in the state
11. ity of the STA Static Timing Analyzer which is part of any synthesis tool to make sure that the glitches die down before the arrival of the next clock edge So if the circuit passed timing design we can be assured that the glitches do not hurt our circuit Single stepping is not a complete solution for debugging as very often we need thousands or millions of clocks needed before the suspected malfunctioning part of the circuit behavior can be encountered For exam ple a real time clock a wall clock may misbehave at the roll over from 23 59 59 to 00 00 00 So it is a good idea to produce MCEN and CCEN We can easily modify the above state diagram to terminate the CCEN or MCEN to force the debounce state machine go back to initial state under any break point condition such as time 23 59 59 EE254L_divider fm 7 19 14 8 15 C 2014 Gandhi Puvvada 9 ee254_ divider_with_single_step ee254_divider_with_single_step DIVDND DIVISOR QUOTIENT REMINDER Go through the files and download the provided bit file and test A l l al Leb i1 L1 E SINGLE STEP SINGLE STEP BtnU SINGLE STEP 3 Qc COMPUTE 3 BtnL START S E Z x OO Note that unlike in the first design ee254_divider_simple we run the core divider in this design at the full speed of 100MHz W amp Qd DONES W BtR ACK i DIVIDEND BtnU BtnL a O x BaD RESET Here in the compute state we single step the division o
12. machine is used to produce glitch free outputs state Name State DPB SCEN MCEN CCEN TB1 TBO initial INI TB1 and TBO are the tie breakers pn ALARE ce to break aliasing in wait half WH output codes Wait quarter WO MCEN state MCEN st CCEN state CCEN st MCEN cont MCEN st Cov r C Ea i ame S me of the earlier MCEN WFCR state WFCR ISE gt Help gt Software Manuals gt Click on Design Verification Design Synthesis in the diagram copy shown on any the side gt XST User guide gt Search for FSM imulation Encoding Design synthesis As shown here we used verilog attributes to j Functional enforce our output coding Through these attributes Era we are informing the tool vendor Xilinx here that Design Static Timing we want the tool to honor and retain our user encod implementation P Analysis Annotation Simulation It is possible to set FSM Encoding option under ISE gt Synthesis XST gt Properties gt HDL Riau options gt FSM Encoding Algorithm User But this will apply to the entire design fsm encoding user lt Verilog attributes are placed in parentheses se tai between asterisks Another example aa a es i zeg lem stater full case parallel case case state FSM Encoding Algorithm Verilog Syntax Example Place FSM Encoding Algorithm immediately before the module or signal declaration fsm encoding auto one
13. o sample and gather signals and show them to us on the PC monitor as waveforms or state listings Let us first talk about single stepping Most common idea is to apply one clock pulse at a time whenever the single step PB is pressed One can think of using a clean glitch free pulse such as DPB as the clock to the system However the problem in FPGA is to put this derived clock on global routing resources in FPGA Spartan 6 FPGA Clocking Resources http www xilinx com support documentation user_guides ug382 pdf If we can not use the global routing resources for our DPB then this DPB reaches different registers in our design at different times and the relative skew difference in the arrival times of these clock pulses Pe P Q causes the circuit to fail For example consider a simple right shift regis cigle 7 ter with progressively delayed clock sent to the right side flip flops SCEN Multi stepping occurs and the shift register fails Hence we designed a better way to implement single stepping We do not use DPB or SCEN SCEN with as the clock but we use SCEN as the clock enable SCEN stands for glitches Single Clock Enable and it is nominally equal in width to a single clock cycle Since it is the clock enable and control the data recirculating mux even if SCEN has some glitches they do not hurt the circuit operation The glitches are in the beginning of the clock and die down by the end of the clock It is the responsibil
14. peration using the SCEN produced out of BtnU Notice the following aspects of the design A The divider and the divider instantiation have a new port pin called SCEN for the top level design to gen erate and pass SCEN pulses Single Clock wide clock enable pulses more accurately data enable pulses as the clock itself 1s not inhibited instantiate the core divider design Note the SCEN SCEN divider divider 1 X1n Xin in in Start Start Ack Ack Clk sys_ clk Reset Reset i Done Done Quotient Quotient Remainder Remainder Q1 Q1 Qc Qc Qd Qd B Single Step Control can easily be exercised on selected states such as the compute state in the divider as shown below The if SCEN clause before begin ensures that 1 all state transformations from the COMPUTE state and 11 all data transformations with in the compute state are under the control of SCEN We do not have to rewrite the state diagram as shown below COMPUTE Original if SCEN Notice SCEN begin state transitions in the control unit if X lt Y state lt DONE S f RTL operations in the Data Path if X lt Y begin if X gt Y SCEN a EE l i X lt X Y Quotient lt Quotient Q lt Q 1 end end EE254L_divider fm 7 19 14 9 15 C 2014 Gandhi Puvvada Questions on ee254_ divider_with_single_step A Is it possible to use SCEN to control one state or a few states MCEN to con
15. r has data available Instead of viewing this as a low active wait it may be easier to view it as a high active GOT signal Notice that the Epp protocol implements the full 4 way handshake Nexys 3 Board Spartan 6 FPGA divider_top File divider_top_with_VIO_multi_step v IOExpansion v from IOExpansion vhd Led 7 0 Lbar 23 0 Btn 15 0 SS ee Format Hexadecimal x ie Cy 3 hs a ag E dwOut 31 0 t E so Cr re fg J A Digilent Adept 7 Cp NEXYS 3 Product Nexys3 Config Memory Test Register I O l File 1 0 1 0 Ex Settings To FPGA Cypress USB interface chip pu_with_VIO_multi_step v es i 5 Light Bar QOQOD0000000000000000000 0d 0F 10 dwIn 3 1 0 0 reg Ver divider_combined_cu_d EE254L_divider fm 7 19 14 11 15 C 2014 Gandhi Puvvada 11 Epp Protocol in short Let us understand a simple processor to memory interface The processor puts out address and a control strobe RD or WR and exchanges data with the addressed location in memory But this involves several signal wires In the case of simpli fied 8088 to memory interface we need 20 address lines A19 A0O 8 data lines D7 DO two control strobes RD and WR In the case of Epp it is desired that the interface has less wires So instead of separate address lines and separate data lines Epp uses one set of 8 data lines which carry data if
16. s and download he provided bit file and test DISPLAY SELECT The switches on the board are not used here 8 bit dividend and 8 bit divisor are set using the 16 switches on Adept IOExpansion The push button mapping 1s as follows a Ls BtnL BtnU BtnR BnD BtnC EE254L_divider fm 7 19 14 14 15 Fa g B ae START ACK QUOTIENT REMAINDER E y m e A a A a A r when btnR is pressed I illiz l I LI a O 2x RESET Ly Ls Ly Ls P FA FS FS C steel EF ka ar mw S m D 3 A Bn A y ae m 3 2 Though not used in this lab C 2014 Gandhi Puvvada ee254 divider_with_VIO_multi_step combined In this example 58H is the dividend and 04H is the divisor The quotient is 16H and the remainder is 00H Can be used to send the Dividend Xin and the Divisor Yin a Digilent Adept CESE 3 connect Nexys3 o or Product Nexys3 combined BtnR_combined BtnD Dividend Divisor Quotient Remainder E 2 To FPGA rom FPGA Light Bar A 0x5804 58041600 UUDDUUUUUUUUUUUU gt m gor loe Send Format Hexadecimal Tonon 6 W Replica of ne LEDs T Switches Buttons 4 see wee da Ooo oooO LC one a eee eee ele o z Can be used to set Divisor Can be usedito set Dividend rt i o Note The 16 switches shall be in down off position if you want to send Xin Yin via the To FPGA facility Similarly if you
17. t MCEN_ Continuous state Here MCEN behaves like CCEN See the output coding table given before LY Nexys3 board clock is at 10OOMHz MCEN_ Cont PB eT 0 084 SCEN_St ey MCEN St PB T 0 168 I lt 0 DPB 1 MCEN 1 CCEN 1 C lt MC 1 Ogy PB T 0 168 28 LLL LLL LLL Sl ay GE RE ASS tl Ae SE a RE eh eg ta NE ep a QA l s b count 0 count 1 e e E count 2 e a count 3 becomes after 8 23 clocks of the CLOCK count 23 becomes 1 after 273 clocks of the CLOCK 2 3 clocks each of 10 ns make 0 084 sec Hence T1 0 084 sec 2 4 clocks each of 10 ns make 0 168 sec Hence T2 0 168 sec Names of the students submitting 1OOMHz frequency corresponds to 10ns clock period 1 EE254L_divider fm 7 19 14 7 15 C 2014 Gandhi Puvvada 8 Single stepping Single stepping and break point setting are used in software or hardware debugging Here we wish to show a hardware debugging mechanism involving single stepping and multi stepping which will lead to setting break points This will be useful particularly when you are interfacing your design with an external system which can not be simulated and proven in simulation Also sometimes there will be simulation synthesis mismatches and this helps in debugging in those situations In later labs we will also show you chipscope to gather hardware signal activity at full speed Chipscope is essentially a logic analyzer placed inside the FPGA chip t
18. th and the control unit can be combined in one case statement under clock as shown in divider _combined_cu_dpu v Notice the lines on the side which avoid unnecessary recirculating muxes We have also provided another file divider_separate_cu_dpu v EE254L_divider fm 7 19 14 1 15 Extract from divider_combined_cu_dpu v begin CU_n DU if Reset begin state lt INITIAL X lt 4 bXXXX 4 bXXXX to avoid Y lt 4 DXXXX Quotient lt 4 XXXX recirculating mux else a I A E aa SSD1 re EE A BtnU BtnL Oo o BtnR C 2014 Gandhi Puvvada Traditional division Division between DPU and between DPU and C CU for HDL coding OFL combinational logic OFL combinational logic is in the CU 1s moved to DPU It is NOT coded explicitly The OFL is implicit in the DPU s RTL in the CASE statement Current State Current State CU CU ee254_divider_simple DIVDND DIVISOR QUOTIENT REMINDER Go through the files and download the provided bit file and test a aa a S BF ae On M mS Ree a E E 3 Qi ANITIAL ca A O Q D 5 W A Qd DONES WE BtnR ACK ms gt BtnU Ww ean em O smr nR BtnL Btn Bt DIVIDEND DIVISOR O sec BMD RESET Questions for the ee254_divider_simple design A What happens if you divide by zero Is the behavior of the quotient digit display on SSD1 different if you attempt to divide 3 by O vs if you attempt to
19. trol another state and further CCEN to control yet another state When we say control a state here we mean control the RTL operations in the state and also the state transitions going away from the state excluding looping around state transitions If we are not going away from the state because of absence of the SCEN pulse then we will remain in the state whether originally there is a loop around state transition or not B Can we choose to place all three states of the divider design under single stepping con g sn SINGLE STEP trol and simultaneously combine Start and Ack under one button say BtnL e Is this just not possible or it works if we produce a BtnL_ SCEN and use it as START as well ze as ACK or Q Can you press two buttons exactly at the same time to 10ns or 5ns accuracy Even if you BnL A press at the same time to that accuracy can you guarantee that they bounce for the same O RECET length of time and the two instances of the debouncing state machine would produce their respective SCEN pulses at the same time C We took time to design output coded state machine with no OFL at all there by avoiding any glitches in the SCEN MCEN etc Are glitches really harmful in our design or we have just shown a way to produce glitch free outputs 10 Epp Interface on Nexys 3 board for communication with the PC Epp stands for Enhanced Parallel Port Epp interface was jie USB Prog Port used to interface PC XT to a
20. umber of these on the Nexys 3 board Besides these we can exchange 32 bit data using the two boxes labeled as To FPGA and From FPGA After instantiating the IO Expansion module defined in IOExpansion v the user logic can send data to the LEDs in the I O Ex tab very much in the same fashion as he would send data to the LEDs on the Nexys 3 board He can read from data on the Virtual switches very much like he reads switches on the Nexys 3 board The Adept GUI uses program driven I O not interrupt driven I O to exchange data It sends and receives data very frequently Cypress USB interface chip Spartan 6 FPGA A Digilent Adept EE254L_divider fm 7 19 14 10 15 C 2014 Gandhi Puvvada A short extract from Digilent manuals EppAstb EppDstb Epp pins in EppWait the ucf file W EppWr W Address Write Address Read The Address Read perhaps is not used in Adept software The following signals make up the interface Name Source Description DBO DB bidir Data bus The host is the source during write cycles and the peripheral is the source during read cycles WRITE hast Transfer direction control Hiah read Low write ASTB host Address strobe Causes data to be read or written to the address register DSTB host Data strobe Causes data to be read or written to a data register WAIT peripheral synchronization signal used to indicate when the peripheral is read to accept data o
21. want to use the switches to send Xin Yin send 0x0 through the 54 _ box Replica of Nexys 3 Buttons Light Bar ae a ee Anqgqgn0 Light Bar Light Bar when not lit DUNUONUN LL EE254L_divider fm 7 19 14 15 15 C 2014 Gandhi Puvvada

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