78M6610+LMU Data Sheet
Slave Packets
The type of slave packet depends upon the type of command from the master device and the successful
execution by the slave device. Standard replies include “Acknowledge” and “Acknowledge with Data”.
ACKNOWLEDGE
without data
ACKNOWLEDGE
with data
BYTE
COUNT
READ
DATA
CHECK
SUM
If no data is expected from the slave or there is a fail code, a single byte reply is sent. If a successfully
decoded command is expected to reply with data, the slave sends a packet format similar to the master
packet where the header is replaced with a Reply Code and the payload contains the read data.
Reply Code
0xAA
Definition
Acknowledge with data
0xAB
Acknowledge with data (half duplex)
Acknowledge without data.
Negative Acknowledge (NACK).
Command not implemented.
Checksum failed.
0xAD
0xB0
0xBC
0xBD
0xBF
Buffer overflow (or packet too long).
- timeout - Any condition too difficult to handle with a reply.
Failure to decode a host packet will cause the selected target to send a fail code (0xB0 – 0xBF)
acknowledgement depending on mode of failure. Masters wishing to simplify could accept any
unimplemented fail code as a Negative Acknowledge.
If no target is selected or the condition of a received packet is uncertain, no reply is sent. Timeouts can
also occur when data is corrupt or no target is selected. The master should implement the appropriate
timeout control logic after approximately 50 byte times at the current baud rate. When a first reply byte is
received, the master should check to see if it is an SSI header or an Acknowledge. If so, the timeout timer
is reset, and each subsequent receive byte will also reset the timer. If no byte is received within the
timeout interval, the master can expect the slave timed out and re-send a new command.
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
