10     REM ***
20     REM Use F2-CP128 as a Simple Modbus RTU Master
30     REM
40     REM Use FC 2 to Read RTU Input Status and put in C0
50     REM Use FC 4 to Read (3) RTU Analog Inputs and put in V2000,2001,2002
60     REM Use FC 5 to Write status of C1 to RTU Output
65     REM Use FC 16 to Write V2010-2015 to RTU Holding Registers
70     REM
80     REM Modbus Slave Address = 1 (RA)
90     REM Baud Rate = 9600 (BAUD)
100    REM Wait for First = 100 ms (WFF)
110    REM Wait for Last = 10 (3.5 Character Times Minimum)
120    REM Modbus Master Port = 2
125    REM ND=On Delay, FD=Off Delay, For Radio Communications
130    REM
140    REM ***
150    REM Allocate String Space and Configure Port 2
160    STRING 2561,255 :  DIM LN(4)
162   RA=1 : BAUD=9600 : WFF=100 : WFL=10
170    SETPORT 2,BAUD,N,8,1,N
175    SETPORT 1,9600,N,8,1,N
180    REM ***
190    REM Initialize Request Strings
195    REM Read Input Status Request String - FC2/Data Address 0/1 Bit
200   $(1)=CHR$(RA)+CHR$(2)+CHR$(0)+CHR$(0)+CHR$(0)+CHR$(1)
201   LN(1)=6
205    REM Read Analog Inputs Request String - FC4/Data Address 0/3 Words
210   $(2)=CHR$(RA)+CHR$(4)+CHR$(0)+CHR$(0)+CHR$(0)+CHR$(3)
211   LN(2)=6
215    REM Write Output Status Request String - FC5/Data Address 0
220   $(3)=CHR$(RA)+CHR$(5)+CHR$(0)+CHR$(0)+CHR$(0)+CHR$(0)
221   LN(3)=6
225    REM Write Multiple Word Request String - FC16/Data Address 0/6 Words
230   $(4)=CHR$(RA)+CHR$(16)+CHR$(0)+CHR$(0)+CHR$(0)+CHR$(6)+CHR$(12)
231   LN(4)=19
290    REM ***
291    REM Configure INPUT statement
295    IF WFL<10 THEN WFL=10 :  REM WFL Must be 10 or greater
297    SETINPUT 1,1,0,255,WFF,WFL
300    REM ***
310    REM Read Input and Copy to C0
320   S=1 :  GOSUB 1000
330    IF ERR<>0 THEN  GOTO 300 :  REM Continuous Retry
340   S205_C(0)=PICK(ASC($(0),4),B(0))
342    REM or S205_VH(40600)=ASC($(0),4)
344    REM If you use line 342 instead of 340 C0-16 will be overwritten
400    REM ***
410    REM Read Three Analog Inputs and Copy to V2000-2003
420   S=2 :  GOSUB 1000
430    IF ERR<>0 THEN  GOTO 400 :  REM Continuous Retry
440   SHARED(128)=ASC($(0),5)
442   SHARED(129)=ASC($(0),4)
444   SHARED(130)=ASC($(0),7)
446   SHARED(131)=ASC($(0),6)
448   SHARED(132)=ASC($(0),9)
450   SHARED(133)=ASC($(0),8)
460    BMOVE W,VH(2000),VH(2003)
500    REM ***
510    REM Read C1 and write to RTU Output
520    IF S205_C(1) THEN ASC($(3),5)=255 ELSE ASC($(3),5)=0
530   S=3 :  GOSUB 1000
540    IF ERR<>0 THEN  GOTO 500 :  REM Continuous Retry
600    REM ***
610    REM Read V2010-V2015 then write to RTU Holding Registers
620    REM V2010-V2015 and put data into request string
622    BMOVE R,VH(2010),VH(2015)
624    FOR X=0 TO 11 STEP 2
625   ASC($(4),8+X)=SHARED(X,H)
626   ASC($(4),9+X)=SHARED(X,L)
628    NEXT X
630   S=4 :  GOSUB 1000
640    IF ERR<>0 THEN  GOTO 600 :  REM Continuous Retry
999    GOTO 300
1000   REM ***
1010   REM Send Request and Get Response in $(0)
1020  $(0)="" : INLEN2=0
1022   PRINT1 "Txd > ";
1024   FOR C=1 TO LN(S) :  PRINT1 HEX$(ASC($(S),C),1)," "; :  NEXT C
1026   REM PRINT1
1030  SYSTEM(2)=NOT(0) :  REM  Turn ON CRC  
1040  DTR2=1 :  DELAY ND
1050   PRINT2 USING(\LN(S)\),$(S);
1060   DELAY FD : DTR2=0
1070   REM INPUT2 ,$(4) : Z=INPLEN : REM Input RS485 Echo REM for RS232 or 422
1071   INPUT2 ,$(0) :  REM Input Response Data
1080  SYSTEM(2)=0 :  REM Turn OFF CRC  
1082   REM PRINT1 "Echo < "; : REM this line and next for RS232 or 422
1084   REM FOR C=1 TO Z : PRINT1 HEX$(ASC($(4),C),1)," "; : NEXT C
1085   PRINT1  :  PRINT1 "Rsp  < ";
1086   FOR C=1 TO INPLEN :  PRINT1 HEX$(ASC($(0),C),1)," "; :  NEXT C
1087   PRINT1 
1089  ERR=0
1090   IF INPLEN=0 THEN  PRINT1 "NO RESPONSE" : ERR=NOT(0) :  RETURN 
1100   IF COMERR2 THEN  PRINT1 "CRC-16 ERROR" : ERR=NOT(0) :  RETURN 
1110   RETURN