SH7144 Datasheet, PDF (471/773 Pages) Renesas Technology Corp – Hitachi SuperH RISC engine

Bit
Initial
Bit Name Value R/W
Description
3 AL
0
R/(W)* Arbitration-lost flag
The AL flag indicates that the device, in master mode, has
failed to acquire bus-master status. The I²C bus interface
monitors the SDA as part of the method of bus arbitration.
When multiple masters make simultaneous attempts to use
the bus, the data on the line will eventually differ, for some of
the masters, from the data issued by the SDA. For such
masters, the AL flag is set to 1 as an indication that the bus is
occupied by another master.
To clear the AL flag, read a 1 from and then write a 0 to it. This
flag is automatically reset when ICDR is written to (during
transmission) or read (during reception).
0: Gaining the bus ownership
[Clearing conditions]
(1) Writing of data to ICDR (during transmission) or reading of
data from ICDR (during reception).
(2) Writing a 0 to this bit after reading it as 1
1: Lost the bus ownership
[Setting conditions]
(1) When the interface is in master-transmission mode, the
SDA value it is generating internally and the value on the
SDA pin do not match on the rising edge of SCL.
(2) When the start condition of another I²C device is detected
(i.e., when the interface is in master-transmission mode
and SCL goes high , and when the internal SDA and the
SDA pin do not match).
Rev. 2.0, 09/02, page 431 of 732