Communication Timing Chart; Composition Of Message; Characteristics - Hitachi 902 Service Manual

16.12.2 Differences in Communication Specification between Conventional Analyzers and Model 902
Conventional Analyzers (Model 7250, 7150, 7050, etc.)
Communication
timing chart
TS
inquiry
Analyzer
HOST
Composition of (1) With less than 255 bytes (TS inquiry, analytical data transfer)
message
STX FN Data filed ETX BCC
(2) With 255 bytes or more (analytical data transfer)
STX FN Data filed ETX BCC

Characteristics

(1) A communication cycle is divided into the first and second halves where TS inquiry
and analytical data transfer are made, respectively.
(2) Function is simple due to discrimination with real-time transfer and batch transfer.
Communication cycle (sec)
TS : Test selecting information
D : Analytical data
(FN: Function No.)
STX FN Data filed ETX BCC
1 sec or more
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Host Manual Drive System (Model 7170/902)
Communication
cycle (sec)
Analyzer
HOST
Conversation
(1) With less than 254 bytes (TS inquiry, analytical data transfer, other)
STX FN Data filed ETX BCC
FR ..... Frame character
' :' ....... Frame character indicating the fianl frame in analytical data transfer
(2) With 254 bytes or more (only transfer of analytical data)
1st Final
STX Frame character Data filed ETX BCC
(1) As a rule, response is made to each request.
(2) Text has a frame No. corresponding to command No. and control code (ACK, NAK) in it for communication control.
(3) Applicable to multiple jobs because there is basically no discrimination between real-time communication (communication
under analysis) and batch communication (specified through screen).
(4) Because protocol need not be changed among instruments, a high maintainability is ensured.
(5) Reducing the burden of host can be expected.
Cluster
1 sec or more
STX : Data filed ETX BCC
(NOTE 1)
NOTES: 1. Usually on receiving response from hos (within 5 sec)
2. 2 sec or more in RESULT ONLY mode