NEC PD75402A - Manual (Page 135)

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CHAPTER 5. PERIPHERAL HARDWARE FUNCTIONS
RESET command
This command is used to change the currently selected slave to non-selected status. All slaves
can be placed in non-selected status by sending the RESET command.
Fig. 5-59 RESET Command Transfer Format
M S
RESET ACK
Command
Remarks M : Output by master
S : Output by slave
➄
CHGMST command
This command passes mastership to the currently selected slave.
Fig. 5-60 CHGMST Command Transfer Format
M S
CHGMST ACK
Command
S S
Data ACK
Data
Remarks M : Output by master
S : Output by slave
When a slave receives the CHGMST command, it determines whether it can assume mastership
and returns data to the master. This data is as follows:
• 0FFH : Change of master possible
• 00H : Change of master not possible
When the slave sends this data, it compares the SIO contents before and after transmission and
if they do not match an error is generated and no ACK is returned.
If there is no error after the 0FFH data has been transmitted, the master operates as a slave and
the slave operates as the master from that point on.
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