NEC V850ES/KE1+ User Manual page 467

STT0
0 Do not generate a start condition.
1 When bus is released (in STOP mode):
Generate a start condition (for starting as master). The SDA0 line is changed from high level to low level
while the SCL0 line is high level and then the start condition is generated. Next, after the rated amount
of time has elapsed, the SCL0 line is changed to low level (wait status).
When a third party is communicating:
• When communication reservation function is enabled (IICF0.IICRSV0 bit = 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 (IICRSV0 bit = 1)
The IICF0.STCF0 bit is set to 1 and the information set (1) to the STT0 bit 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 when the ACKE0 bit has been
cleared to 0 and slave has been notified of final reception.
For master transmission: A start condition may not be generated normally during the acknowledgment 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 the SPT0 bit.
• When the STT0 bit is set to 1, setting the STT0 bit to 1 again is disabled until the setting is cleared to 0.
Condition for clearing (STT0 bit = 0)
• When the STT0 bit is set to 1 in the communication
reservation disabled status
• Cleared by loss in arbitration
• Cleared when start condition is generated by master
device
• When the LREL0 bit = 1 (exit from communications)
• When the IICE0 bit changes from 1 to 0 (operation stop)
• Reset
Remark The STT0 bit is 0 if it is read after data setting.
2
CHAPTER 16 I C BUS
Start condition trigger
Condition for setting (STT0 bit = 1)
• Set by instruction
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