RL78/G1P
CHAPTER 12 SERIAL INTERFACE IICA
R01UH0895EJ0100 Rev.1.00
474
Nov 29, 2019
Figure 12-6. Format of IICA Control Register n0 (IICCTLn0) (3/4)
STTn
Note
Start condition trigger
0
Do not generate a start condition.
1
When bus is released (in standby state, when IICBSYn = 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 (IICRSVn = 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 (IICRSVn = 1)
Even if this bit is set (1), the STTn bit is cleared and the STTn clear flag (STCFn) 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 the
ACKEn bit 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 stop condition trigger (SPTn).
Once STTn is set (1), setting it again (1) before the clear condition is met is not allowed.
Condition for clearing (STTn = 0)
Condition for setting (STTn = 1)
Cleared by setting the STTn bit to 1 while
communication reservation is prohibited.
Cleared by loss in arbitration
Cleared after start condition is generated by master
device
Cleared by LRELn = 1 (exit from communications)
When IICEn = 0 (operation stop)
Reset
Set by instruction
Note
The signal of this bit is invalid while IICEn is 0.
Remarks 1.
Bit 1 (STTn) becomes 0 when it is read after data setting.
2.
IICRSVn: Bit 0 of IIC flag register n (IICFn)
STCFn:
Bit 7 of IIC flag register n (IICFn)
3.
n = 0, 1