
CHAPTER 18 I
2
C BUS
User
’
s Manual U15862EJ3V0UD
553
(3/4)
ACKEn
Acknowledge control
0
Disable acknowledge.
1
Enable acknowledge. During the ninth clock period, the SDAn line is set to low level. However, the ACK is
invalid during address transfers and is valid when EXCn = 1.
Condition for clearing (ACKEn = 0)
Note
Condition for setting (ACKEn = 1)
Cleared by instruction
When RESET is input
Set by instruction
STTn
Start condition trigger
0
Does not generate a start condition.
1
When bus is released (in STOP mode):
Generates a start condition (for starting as master). The SDAn 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, SCLn
is changed to low level.
When bus is not used:
When communication reservation function is enabled (IICRSVn = 0)
Functions as the start condition reservation flag. When set, automatically generates a start condition
after the bus is released.
When communication reservation function is disabled (IICRSVn = 1)
The STCFn flag is set. 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 during transfer. Can be set only when ACKEn has been set to 0 and slave
has been notified of final reception.
For master transmission: A start condition cannot be generated normally during the ACKn period. Set during the wait
period.
Cannot be set at the same time as SPTn
Condition for clearing (STTn = 0)
Condition for setting (STTn = 1)
Cleared by instruction
Cleared by loss in arbitration
Cleared after start condition is generated by master
device
When LRELn = 1
When IICEn = 0
Cleared when RESET is input
Set by instruction
Note
This flag
’
s signal is invalid when IICEn = 0.
Remarks 1.
Bit 1 (STTn) is 0 if it is read after data setting.
2.
IICRSVn: Bit 0 of IIC flag register n (IICFn)
STCFn: IICRSVn: Bit 7 of IIC flag register n (IICFn)