NEC 78K0 Series User Manual page 415

Figure 17-5. Format of IIC Control Register 0 (IICC0) (3/4)
Note
STT0
0 Do not generate a start condition.
1 When bus is released (in STOP mode):
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.
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 information that is set (1) to 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)
• 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
Note This flag's signal is invalid when IICE0 = 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)
CHAPTER 17 SERIAL INTERFACE IIC0
Start condition trigger
Condition for setting (STT0 = 1)
• Set by instruction
Preliminary User's Manual U17260EJ3V1UD
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