CHAPTER 14 SERIAL INTERFACE IIC0
User’s Manual U17894EJ9V0UD
539
Figure 14-6. Format of IIC Control Register 0 (IICC0) (3/4)
STT0
Note
Start condition trigger
0
Do not generate a start condition.
1
When bus is released (in standby state, when IICBSY = 0):
Generate a start condition (for starting as master). When the SCL0 line is high level, the SDA0 line is
changed from high level to low level and then the start condition is generated. Next, after the rated
amount of time has elapsed, SCL0 is changed to low level (wait state).
When a third party is communicating:
When communication reservation function is enabled (IICRSV = 0)
Functions as the start condition reservation flag. When set to 1, automatically generates a start
condition after the bus is released.
When communication reservation function is disabled (IICRSV = 1)
STCF is set to 1 and STT0 is cleared. No start condition is generated.
In the wait state (when master device):
Generates a restart condition after releasing the wait.
Cautions concerning set timing
For master reception:
Cannot be set to 1 during transfer. Can be set to 1 only in the waiting period when
ACKE0 has been cleared to 0 and slave has been notified of final reception.
For master transmission: A start condition cannot be generated normally during the acknowledge period. Set to 1
during the wait period that follows output of the ninth clock.
Cannot be set to 1 at the same time as SPT0.
Setting STT0 to 1 and then setting it again before it is cleared to 0 is prohibited.
Condition for clearing (STT0 = 0)
Condition for setting (STT0 = 1)
Cleared by setting SST0 to 1 while communication
reservation is prohibited.
Cleared by loss in arbitration
Cleared after start condition is generated by master
device
Cleared by LREL0 = 1 (exit from communications)
When IICE0 = 0 (operation stop)
Reset
Set by instruction
Note
The signal of this bit is invalid while IICE0 is 0.
Remarks 1. Bit 1 (STT0) becomes 0 when it is read after data setting.
2. IICRSV: Bit 0 of IIC flag register (IICF0)
STCF:
Bit 7 of IIC flag register (IICF0)
<R>
