CHAPTER 19 IEBus CONTROLLER (V850/SB2)
User’s Manual U13850EJ4V0UM
467
(8) IEBus unit status register (USR)
Figure 19-22. IEBus Unit Status Register (USR)
After reset: 00H
R
Address: FFFFF3EEH
7
<6>
<5>
<4>
<3>
<2>
1
0
USR
0
SLVRQ
ARBIT
ALLTRNS
ACK
LOCK
0
0
SLVRQ
Slave request flag
0
No request from master to slave
1
Request from master to slave
ARBIT
Arbitration result flag
0
Arbitration win
1
Arbitration loss
ALLTRNS
Broadcasting communication flag
0
Individual communication status
1
Broadcasting communication status
ACK
ACK transmission flag
0
NACK transmitted
1
ACK transmitted
LOCK
Lock status flag
0
Unit unlocked
1
Unit locked
(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 broadcasting 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.
Содержание MPD703030A
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