RL78/G1P
CHAPTER 12 SERIAL INTERFACE IICA
R01UH0895EJ0100 Rev.1.00
478
Nov 29, 2019
Figure 12-7. Format of IICA Status Register n (IICSn) (3/3)
ACKDn
Detection of acknowledge (ACK)
0
Acknowledge was not detected.
1
Acknowledge was detected.
Condition for clearing (ACKDn = 0)
Condition for setting (ACKDn = 1)
When a stop condition is detected
At the rising edge of the next byte’s first clock
Cleared by LRELn = 1 (exit from communications)
When the IICEn bit changes from 1 to 0 (operation
stop)
Reset
After the SDAAn line is set to low level at the rising
edge of SCLAn line’s ninth clock
STDn
Detection of start condition
0
Start condition was not detected.
1
Start condition was detected. This indicates that the address transfer period is in effect.
Condition for clearing (STDn = 0)
Condition for setting (STDn = 1)
When a stop condition is detected
At the rising edge of the next byte’s first clock
following address transfer
Cleared by LRELn = 1 (exit from communications)
When the IICEn bit changes from 1 to 0 (operation
stop)
Reset
When a start condition is detected
SPDn
Detection of stop condition
0
Stop condition was not detected.
1
Stop condition was detected. The master device’s communication is terminated and the bus is
released.
Condition for clearing (SPDn = 0)
Condition for setting (SPDn = 1)
At the rising edge of the address transfer byte’s first
clock following setting of this bit and detection of a
start condition
When the WUPn bit changes from 1 to 0
When the IICEn bit changes from 1 to 0 (operation
stop)
Reset
When a stop condition is detected
Remarks 1.
LRELn: Bit 6 of IICA control register n0 (IICCTLn0)
IICEn:
Bit 7 of IICA control register n0 (IICCTLn0)
2.
n = 0, 1
12.3.4 IICA flag register n (IICFn)
This register sets the operation mode of I
2
C and indicates the status of the I
2
C bus.
The IICFn register can be set by a 1-bit or 8-bit memory manipulation instruction. However, the STTn clear flag
(STCFn) and I
2
C bus status flag (IICBSYn) bits are read-only.
The IICRSVn bit can be used to enable/disable the communication reservation function.
The STCENn bit can be used to set the initial value of the IICBSYn bit.
The IICRSVn and STCENn bits can be written only when the operation of I
2
C is disabled (bit 7 (IICEn) of IICA control
register n0 (IICCTLn0) = 0). When operation is enabled, the IICFn register can be read.
Reset signal generation clears this register to 00H.