Transfer Format Of The Reset Command; Transfer Format Of The Chgmst Command - NEC PD750004 User Manual

µPD750008 USER'S MANUAL
<4> RESET command
The RESET command changes the currently selected slave to a non-selected slave. When
a RESET command is transmitted, any slave can be placed in the non-selected state.
Remark M: Output by the master
<5> CHGMST command
The CHGMST command passes the master authority to the currently selected slave.
Remark M: Output by the master
When the slave receives a CHGMST command, the slave returns one of the following data
to the master after checking whether the slave can receive the master authority:
• 0FFH: Master changeable
• 00H:
The slave compares the contents of SIO before transfer with the contents of SIO after transfer.
If the contents of SIO disagree with each other, an error occurs; ACK is not returned in this
case.
If the master receives 0FFH, the master returns ACK to the slave, and starts to operate as
a slave. The slave which transmitted 0FFH starts to operate as the master when it receives
ACK.
(iv) Error occurrence
If a communication error occurs, the operation described below is performed.
The slave reports the occurrence of an error by not returning ACK to the master. If an error
occurs during reception of data, the slave sets the status bit for indicating error occurrence,
and cancels all command processing being performed.
When the transmission of one byte is completed, the master checks for ACK from the slave.
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Figure 5-77. Transfer Format of the RESET Command
M
RESET
Command
S: Output by the slave
Figure 5-78. Transfer Format of the CHGMST Command
M
CHGMST
Command
S: Output by the slave
Master not changeable
S
ACK
S S
ACK Data
Data
S
ACK