406
time a frame is received and checking the result against the FCS that is included
in the frame makes it possible to check for data errors in the frame.
FCS
:
↵
0
1
R
R
0
@
0
0
1
4
2
Text
Node no.
Header code
FCS calculation range
Terminator
@
40
0100
0000
EOR
1
31
0011
0001
EOR
0
30
0011
0000
EOR
R
52
0101
0010
1
31
0011
0001
0100
0010
↓
↓
Converted to hexadecimal.
4
2
Handled as ASCII characters.
ASCII code
Calculation
result
Example Program for FCS
This example shows a BASIC subroutine program for executing an FCS check
on a frame received by the host computer.
400 *FCSCHECK
410 L=LEN(RESPONSE$) ’
Data transmitted and received
. . . . . . . . . . .
420 Q=0:FCSCK$=“ ”
430 A$=RIGHT$(RESPONSE$,1)
440 PRINT RESPONSE$,AS,L
450 IF A$=”*” THEN LENGS=LEN(RESPONSE$)-3
ELSE LENGS=LEN(RESPONSE$)-2
460 FCSP$=MID$(RESPONSE$,LENGS+1,2) ’
FCS data received
. . . .
470 FOR I=1 TO LENGS ’
Number of characters in FCS
. . . . . . . . . . .
480 Q=ASC(MID$(RESPONSE$,I,1)) XOR Q
490 NEXT I
500 FCSD$=HEX$(Q)
510 IF LEN(FCSD$)=1 THEN FCSD$=”0”+FCSD$ ’
FCS result
520 IF FCSD$<>FCSP$ THEN FCSCK$=”ERR”
530 PRINT“FCSD$=”;FCSD$,“FCSP$=”;FCSP$,“FCSCK$=”;FCSCK$
540 RETURN
Note
1. Normal reception data includes the FCS, delimiter or terminator, and so on.
When an error occurs in transmission, however the FCS or some other data
may not be included. Be sure to program the system to cover this possibility.
2. In this program example, the CR code (CHR$(13)) is not entered for RE-
SPONSE$. When including the CR code, make the changes in lines 430
and 450.
11-2-2 Commands from the PC
In host link communications, commands are ordinarily sent from the host com-
puter to the PC, but it is also possible for commands to be sent from the PC to the
host computer. In Host Link Mode, any data can be transmitted from the PC to
the host computer. To send a command to the host computer, use the TRANS-
MIT instruction (TXD(--)) in the PC program in Host Link Mode.
TXD(––) outputs data from the specified port (the RS-232C port or the peripher-
al port). Refer to page 299 for details on using TXD(––).
Command and Response Formats
Section 11-2
Содержание SYSMAC C200HS
Страница 1: ...Cat No W235 E1 05 C200HS SYSMAC Programmable Controllers...
Страница 2: ...C200HS Programmable Controllers Operation Manual Revised February 2002...
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Страница 379: ...371 SR word Corresponding key s Bit 279 03 04 05 3 06 07 VER 08 09 Monitoring Operation and Modifying Data Section 7 1...
Страница 470: ...468 Programmer Program Date Page Word Contents Notes Word Contents Notes Data Storage...
Страница 471: ...469 Programmer Program Date Page TC address T or C Set value Notes TC address T or C Set value Notes Timers and Counters...