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2 Simple Application Controllers
The Command String 7
7 - 4
Note:
1 ) Format B WRITE/(RUN/STOP) operation can produce an error code even though a
standard complete flag has been sent. If the Transmit message contains the correct syntax
then a complete flag will be sent, however, if the reply data is corrupt then a NAK message
will be generated.
2 ) The write message string is intended for BIT data accessing, therefore, only one byte has
been allocated to the Device Status setting. To write to WORD data, 2 bytes must be
allocated to the Device setting. Thus, caution in setting the No. of communication bytes
and the sum code check must be taken.
Read/Write operation for Format B follows a different structure to Format A. Format B uses a
more complex string to access internal devices. However, the write operation contains the
Device Status parameter used to indicate the ON/OFF state of the intended device.
Time Switch settings follow Format B protocol, however, the structure and content of the string
differs from the standard READ/WRITE mode operation. Refer to section 7.6.5 for further
detailed information concerning Time Switch settings for Format B.
Format B READ Mode Format B WRITE mode (BIT)
Control Code
No. of Communication bytes
Format No.
Station No.
Command
No. of devices
Device No. (LB)
Device No. (HB)
Control Code
Sum Check (LB)
Sum Check (HB)
Device Status
Device Code
Control Code
No. of Communication bytes
Format No.
Station No.
Command
No. of devices
Device Code
Device No. (LB)
Device No. (HB)
Control Code
Sum Check (LB)
Sum Check (HB)