UPD78F1502AGK-GAK-AX Datasheet, PDF (603/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 15 SERIAL INTERFACE IICA
Figure 15-6. Format of IICA Control Register 0 (IICCTL0) (3/4)
STT^Note
Start condition trigger
0
Do not generate a start condition.
1
When bus is released (in standby state, when IICBSY = 0):
If this bit is set (1), a start condition is generated (startup as the master).
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)
Even if this bit is set (1), the STT bit is cleared and the STT clear flag (STCF) is set (1). 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 ACKE
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 SPT.
• Setting STT to 1 and then setting it again before it is cleared to 0 is prohibited.
Condition for clearing (STT = 0)
• Cleared by setting STT to 1 while communication
reservation is prohibited.
• Cleared by loss in arbitration
• Cleared after start condition is generated by master
device
• Cleared by LREL = 1 (exit from communications)
• When IICE = 0 (operation stop)
• Reset
Condition for setting (STT = 1)
• Set by instruction
Note The signal of this bit is invalid while IICE0 is 0.
Remarks 1. Bit 1 (STT) becomes 0 when it is read after data setting.
2. IICRSV: Bit 0 of IIC flag register (IICF)
STCF: Bit 7 of IIC flag register (IICF)
R01UH0004EJ0501 Rev.5.01
587
Jun 20, 2011