Datasheet

V850ES/JG3 CHAPTER 17 I
2
C BUS
R01UH0015EJ0300 Rev.3.00 Page 602 of 870
Sep 30, 2010
17.16.3 Slave operation
The following shows the processing procedure of the slave operation.
Basically, the operation of the slave device is event-driven. Therefore, processing by an INTIICn interrupt (processing
requiring a significant change of the operation status, such as stop condition detection during communication) is necessary.
The following description assumes that data communication does not support extension codes. Also, it is assumed that
the INTIICn interrupt servicing performs only status change processing and that the actual data communication is
performed during the main processing.
Figure 17-20. Software Outline During Slave Operation
I
2
C
INTIICn signal
Setting, etc.
Setting, etc.
Flag
Data
Main processing
Interrupt servicing
Therefore, the following three flags are prepared so that the data transfer processing can be performed by transmitting
these flags to the main processing instead of INTIICn signal.
(1) Communication mode flag
This flag indicates the following communication statuses.
Clear mode: Data communication not in progress
Communication mode: Data communication in progress (valid address detection stop condition detection, ACK from
master not detected, address mismatch)
(2) Ready flag
This flag indicates that data communication is enabled. This is the same status as an INTIICn interrupt during normal
data transfer. This flag is set in the interrupt processing block and cleared in the main processing block. The ready
flag for the first data for transmission is not set in the interrupt processing block, so the first data is transmitted without
clear processing (the address match is regarded as a request for the next data).
(3) Communication direction flag
This flag indicates the direction of communication and is the same as the value of IICSn.TRCn bit.
The following shows the operation of the main processing block during slave operation.
Start I
2
C0n and wait for the communication enabled status. When communication is enabled, perform transfer using the
communication mode flag and ready flag (the processing of the stop condition and start condition is performed by
interrupts, conditions are confirmed by flags).
For transmission, repeat the transmission operation until the master device stops returning ACK. When the master
device stops returning ACK , transfer is complete.