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CHAPTER 17
IEBus CONTROLLER (
PD178096A, 178098A, 178F098 ONLY)
User’s Manual U12790EJ2V0UD
(8) IEBus unit status register (USR)
Figure 17-22. Format of IEBus Unit Status Register (USR)
(a) Slave request flag (SLVRQ)...Bit 6
A flag indicating whether there has been a slave request from the master.
<Set/reset conditions>
Set:
When the unit is requested as a slave (if the received slave address and unit UAR match during
individual communication reception, or if the higher 4 bits of the received slave address match or
if the received slave address is FFFH during broadcast communication reception), this flag is set
by hardware when the acknowledge period of the slave address field starts.
Reset: This flag is reset by hardware when the unit is not requested as a slave. The reset timing is the
same as the set timing. If the unit is requested as a slave immediately after communication has
been correctly received (when the SLVRQ bit is set), and if a parity error occurs in the slave address
field for that communication, the flag is not reset.
0
No request from master to slave
Request from master to slave
SLVRQ
0
1
Slave request flag
USR
SLVRQ
ARBIT
ALLTRNS
ACK
LOCK
0
Arbitration win
Arbitration loss
ARBIT
0
1
Arbitration result flag
After reset: 00H
R
Address: FFBBH
Individual communication status
Broadcast communication status
ALLTRNS
0
1
Broadcast communication flag
NACK transmitted
ACK transmitted
ACK
0
1
ACK transmission flag
Unit unlocked
Unit locked
LOCK
0
1
Lock status flag
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