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Bit 2 Bus Busy (BBSY): The BBSY flag can be read to check whether the I
is busy or free. In master mode, this bit is also used to issue start and stop conditions.
A high-to-low transition of SDA while SCL is high is recognized as a start condition, setting
BBSY to 1. A low-to-high transition of SDA while SCL is high is recognized as a stop condition,
clearing BBSY to 0.
To issue a start condition, use a MOV instruction to write 1 in BBSY and 0 in SCP. A retransmit
start condition is issued in the same way. To issue a stop condition, use a MOV instruction to
write 0 in BBSY and 0 in SCP.
It is not possible to write to BBSY in slave mode; the I
transmit mode before issuing a start condition. MST and TRS should both be set to 1 before
writing 1 in BBSY and 0 in SCP.
Bit 2
BBSY
Description
0
Bus is free
[Clearing condition]
When a stop condition is detected
1
Bus is busy
[Setting condition]
When a start condition is detected
Bit 1 I
2
C Bus Interface Interrupt Request Flag (IRIC): Indicates that the I
issued an interrupt request to the CPU. IRIC is set to 1 at the end of a data transfer, when a slave
address or general call address is detected in slave receive mode, when bus arbitration is lost in
master transmit mode, and when a stop condition is detected. IRIC is set at different times
depending on the FS bit in SAR and the WAIT bit in ICMR. See section 23.3.6, IRIC Setting
Timing and SCL Control. The conditions under which IRIC is set also differ depending on the
setting of the ACKE bit in ICCR.
IRIC is cleared by reading IRIC after it has been set to 1, then writing 0 in IRIC.
When the DTC is used, IRIC is cleared automatically and transfer can be performed continuously
without CPU intervention.
Rev. 1.0, 02/00, page 476 of 1141
2
C bus interface must be set to master
2
C bus (SCL, SDA)
(Initial value)
2
C bus interface has
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