CHAPTER 17 SERIAL INTERFACE IIC0
Preliminary User’s Manual U17260EJ3V1UD
417
(2) IIC status register 0 (IICS0)
This register indicates the status of I
2
C.
IICS0 is read by a 1-bit or 8-bit memory manipulation instruction only when STT0 = 1 and during the wait
period.
Reset signal generation sets IICS0 to 00H.
Caution If data is read from IICS0, a wait cycle is generated. Do not read data from IICS0 when the
CPU is operating on the subsystem clock and the peripheral hardware clock is stopped. For
details, see CHAPTER 31 CAUTIONS FOR WAIT.
Figure 17-6. Format of IIC Status Register 0 (IICS0) (1/3)
Address: FFAAH
After reset: 00H
R
Symbol
<7> <6> <5> <4> <3> <2> <1> <0>
IICS0 MSTS0 ALD0 EXC0 COI0 TRC0 ACKD0 STD0 SPD0
MSTS0 Master
device
status
0
Slave device status or communication standby status
1
Master device communication status
Condition for clearing (MSTS0 = 0)
Condition for setting (MSTS0 = 1)
•
When a stop condition is detected
•
When ALD0 = 1 (arbitration loss)
•
Cleared by LREL0 = 1 (exit from communications)
•
When IICE0 changes from 1 to 0 (operation stop)
•
Reset
•
When a start condition is generated
ALD0
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”. MSTS0 is cleared.
Condition for clearing (ALD0 = 0)
Condition for setting (ALD0 = 1)
•
Automatically cleared after IICS0 is read
Note
•
When IICE0 changes from 1 to 0 (operation stop)
•
Reset
•
When the arbitration result is a “loss”.
EXC0
Detection of extension code reception
0
Extension code was not received.
1
Extension code was received.
Condition for clearing (EXC0 = 0)
Condition for setting (EXC0 = 1)
•
When a start condition is detected
•
When a stop condition is detected
•
Cleared by LREL0 = 1 (exit from communications)
•
When IICE0 changes from 1 to 0 (operation stop)
•
Reset
•
When the higher four bits of the received address data is
either “0000” or “1111” (set at the rising edge of the
eighth clock).
Note
This register is also cleared when a 1-bit memory manipulation instruction is executed for bits other
than IICS0. Therefore, when using the ALD0 bit, read the data of this bit before the data of the other
bits.
Remark
LREL0: Bit 6 of IIC control register 0 (IICC0)
IICE0: Bit 7 of IIC control register 0 (IICC0)