
B-63322EN-1/01 5. EXPANSION PROTOCOL A
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b) End packet : FFh
The end packet is transmitted by setting the packet No. to
FFh. The data part of end packet is considered to be the
effective data. However, the end packet received after
transmitting <CAN> ignores the data part.
This allows the expansion protocol A mode to be ended and
the normal protocol A mode is initiated.
However, when the checksum error is detected at the end
packet, the before packet No. +1 is transmitted as the end
packet No. to the host computer with monitor packet
<NAK> of retransmission request. (Note)
The host computer should shift to the protocol A when the
command of protocol A is received after transmitting the
end packet.
NOTE
If FFh is assigned to the first packet, packet No. 0 is
transmitted to the host computer with <NAK>, since this
packet is the last packet.
c) Invalid packet : Other than above
Transmit this invalid packet with the dummy data of
“256*n” bytes when the time out may occur since time is
required for editing of NC data transmitted by the host
computer.
The remote buffer is processed as an invalid packet.
3) Checksum
The checksum is obtained by adding the NC data to the packet
No. in units of byte and then expressing the 1 byte data produced
by neglecting the overflow above 8 bits out of the total value
above using ASCII 2-byte code.
4) End code
The end code should be the ASCII code CR (0Dh).