A4. SERIAL COMMUNICATIONS PROTOCOL
A-9
Power Supply Unit
INSTRUCTION MANUAL
A
A4.3 Command to Answer Time-out: 1 sec.
Delays between COMMAND and ANSWER messages, longer that 1 sec., shall be considered
as a transmission line failure and special considerations should be made to re-send the
message.
The power supply re-sends a COMMAND, if it does not receive and ANSWER within a one
second period.
A4.4 Power Supply Command Send Retry Cycles: 5
If the power supply does not receive and answer to a command, within one second, it will re-
send the same command up to a maximum of five times.
A4.5 Command Transmission Specification
A command sent before an answer is sent, will be ignored by the power supply, until a reply to
the first command is sent. However, this does not apply after a transmission time-out occurs
between command and answer. (If processing is performed normally, an answer is returned
within 100 msec.)
A4.6 Receiving Sequence
The character string from the power supply unit is received after the COMMAND character
string is sent. When the carriage return code (0dH) is received, the received character string is
checked from the beginning and the portion from the initial command header "MJ" to the carriage
return code received last is processed as an answer.
Initialize the receive buffer after the answer character string is acquired from the receive buffer.
The read user memo (described below) may receive the same "MJ" as the command header
character string in the answer character string. Therefore, interpret the character string from the
first "MJ" appearing in the receive buffer to the carriage return as the answer character string.
A4.7 Using the Checksum Byte
Always calculate the checksum for a received character string and compare it with the
checksum byte data to confirm that the character string was received correctly. Conduct error
processing such as re-sending the command when a character string is received with an
incorrect checksum.
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