RL78/G1P
CHAPTER 12 SERIAL INTERFACE IICA
R01UH0895EJ0100 Rev.1.00
476
Nov 29, 2019
12.3.3 IICA status register n (IICSn)
This register indicates the status of I
2
C.
The IICSn register is read by a 1-bit or 8-bit memory manipulation instruction only when STTn = 1 and during the wait
period.
Reset signal generation clears this register to 00H.
Caution Reading the IICSn register while the address match wakeup function is enabled (WUPn = 1) in STOP
mode is prohibited. When the WUPn bit is changed from 1 to 0 (wakeup operation is stopped),
regardless of the INTIICAn interrupt request, the change in status is not reflected until the next start
condition or stop condition is detected. To use the wakeup function, therefore, enable (SPIEn = 1)
the interrupt generated by detecting a stop condition and read the IICSn register after the interrupt
has been detected.
Remark
STTn: Bit 1 of IICA control register n0 (IICCTLn0)
WUPn: Bit 7 of IICA control register n1 (IICCTLn1)
Figure 12-7. Format of IICA Status Register n (IICSn) (1/3)
Address: FFF51H (IICS0), FFF55H (IICS1)
After reset: 00H R
Symbol
<7> <6> <5> <4> <3> <2> <1> <0>
IICSn MSTSn ALDn EXCn COIn TRCn ACKDn STDn SPDn
MSTSn
Master status check flag
0
Slave device status or communication standby status
1
Master device communication status
Condition for clearing (MSTSn = 0)
Condition for setting (MSTSn = 1)
When a stop condition is detected
When ALDn = 1 (arbitration loss)
Cleared by LRELn = 1 (exit from communications)
When the IICEn bit changes from 1 to 0 (operation
stop)
Reset
When a start condition is generated
ALDn
Detection of arbitration loss
0
This status means either that there was no arbitration or that the arbitration result was a “win”.
1
This status indicates the arbitration result was a “loss”. The MSTSn bit is cleared.
Condition for clearing (ALDn = 0)
Condition for setting (ALDn = 1)
Automatically cleared after the IICSn register is
read
Note
When the IICEn bit changes from 1 to 0 (operation
stop)
Reset
When the arbitration result is a “loss”.
Note
This register is also cleared when a 1-bit memory manipulation instruction is executed for bits other
than the IICSn register. Therefore, when using the ALDn bit, read the data of this bit before the data
of the other bits.
Remarks 1.
LRELn: Bit 6 of IICA control register n0 (IICCTLn0)
IICEn: Bit 7 of IICA control register n0 (IICCTLn0)
2.
n = 0, 1