YOKOGAWA F3LC11-1F, User Manual

Page: 128 / 202

B2-8
IM 34M6H41-02E 2nd Edition : Aug. 1, 2005-00
Checksum Calculation
The checksum is obtained by simply summing the ASCII codes of the character portion
of a command or response.
We show below how the checksum is calculated on the sending end (command).
(1) Add the ASCII codes of characters, starting with the character following the STX
character (that is, the first character of the station number) until the character
preceding the checksum (that is, the last character of the command parameters).
(2) Extract the low order byte of the sum.
(3) Express the hexadecimal value of the byte as a character string (2 characters) to
obtain the checksum.
(The checksum is also represented as a string of 2 characters).
(Example)
Reading 16 bits from X00201 from CPU number 1 of station number 01 with a 100
ms response wait time (with the ending character specified as “CR”)
6
36
B
42
STX
0
30
1
31
0
30
1
31
A
41
R
52
B
42
D
44
X
58
0
30
0
30
2
32
0
30
1
31
,
2C
1
31
9
39 02
ETX
03
CR
0D
Send text
(char string)
ASCII code
(hexadecimal)
Checksum
calculation range
Check
sum
End
char.
The checksum is the low-order byte ($B9) of the calculation result ($3B9), expressed as a string "B9".
30+31+30+31+41+42+52+44+58+30+30+32+30+31+2C+31+36=3B9 (hexadecimal)
FA20005.VSD
Command Reference
For details on the PC link commands, refer to the “Personal Computer Link Command”
manual (IM34M6P41-01E).