Omron E5AF, Operation Manual

Page: 28 / 82

Controller numbers correspond to unit numbers in a PC system. When as-
signing Controller numbers for several Controllers, be sure to avoid duplica-
tion of the settings.
3--5--2 Blocks
The block transmitted from the host computer is referred to as a command
block.
Blocks sent from the Temperature Controller are called response blocks.
One block begins with the start character “@” and communications address,
and ends with the FCS and a terminator. Data characters are in ASCII.
8 bit
*
Terminator Text
FCS range of calculation
@ Controller no. X X X X
X10
1
X10
0
(00 to 99) Header
code
FCS
The FCS (frame check sequence) is formed by converting the 8-bit data ob-
tained by taking the exclusive-OR of @ to the last text character into two
ASCII characters. Be sure to attach the FCS to the end of the text.
FCS Calculation Example
@ 0 0 R U 0 1 4 6
Controller
no.
Header
code
Text FCS
*
40H 30H 30h 52H 55H 30H 31H 34H 36H
ASCII code
FCS = 40H (+) 30H (+) 30H (+) 52H (+) 55H (+) 30H (+) 31H = 46H
(Converted into ASCII code 34H + 36H)
(+) is exclusive-OR, H is hexadecimal code.
3--5--3 Error Control
E5AF/E5EF errors must be corrected at the host computer. The host comput-
er controls the following error recovery procedures:
Errors in transmission can be detected in the following ways.
1. Character checks (check of each character)
•
Vertical parity check (even): This is an exclusive-OR check for each char-
acter.
•
Framing check: This detects the 0 bit in a stop bit and determines it to be an
error.
•
Overrun check. Overrun occurs when the next character is received while
the current character is being processed.
2. Block checks (check of each block)
•
Format check: Command format structure is checked.
•
Register data check: The range of values such as the channel numbers or
set value is checked.
Section 3--5