Vidikron VP-60 - Manual (Page 81)

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Communication Format
8 bit 8 bit 8 bit 8 bit 8 bit 8 bit • • 8 bit 8 bit
Command 1
Unit ID 1
Unit ID 2
Command 2
Data length
Data
Check sum
Command 1
Command 1, along with command 2, is a number used to
distinguish each command. In the case of ACK, when the lower
order 4 bits is FH (as in 3FH and 7FH), this indicates that the
commands and data of the supported equipment have been
received. When the lower order 4 bits is BH (as in 3BH and 7BH),
this indicates that unsupported commands and data have been
received.
Unit ID 1 and Unit ID 2
Unit ID 1 and unit ID 2 are numbers used to identify the
equipment that is to be connected. 60H is used for the plasma
monitor and 80H is used for external control equipment such as a
personal computer.
1) Unit ID 1: Indicates the equipment sending the signal
2) Unit ID 2: Indicates the equipment receiving the signal
Command 2
Command 2, along with command 1, is a number used to
distinguish each command.
Check Sum (CKS), Error Processing, and ACK
1) The check sum described below and RS-232C odd parity
are used together for a check of the received data. The check
sum is the lower order 8 bits of one frame of sent or received
data comprising the sum total of Command 1, Unit ID 1 and
2, Command 2, Data Length, and Data.
Check Sum Example
DFH 80H 60H 47H 01H 01H 08H
Com-
mand 1
Unit
ID 1
Unit
ID 2
Com-
mand 2
Data
Length
Data Check
Sum
Total 208H
2) Error Processing
* When the communication interval is vacant for more than 4
ms, thereafter a received Command 1 will be recognized. If, at
this time, meaningful data cannot be recognized, that data will
not be recognized (as valid data).
* An ACK will not be returned unless the receive data error, the
check sum error, and the receive data are all taken in.
External Controls