CHAPTER 15 SERIAL INTERFACE IICA
Page 475 of 920
(3) Slave operation
The processing procedure of the slave operation is as follows.
Basically, the slave operation is event-driven. Therefore, processing by the INTIICAn interrupt (processing
that must substantially change the operation status such as detection of a stop condition during
communication) is necessary.
In the following explanation, it is assumed that the extension code is not supported for data communication.
It is also assumed that the INTIICAn interrupt servicing only performs status transition processing, and that
actual data communication is performed by the main processing.
Therefore, data communication processing is performed by preparing the following three flags and passing
them to the main processing instead of INTIICAn.
<1> Communication mode flag
This flag indicates the following two communication statuses.
•Clear mode:
Status in which data communication is not performed
•Communication mode: Status in which data communication is performed (from valid address
detection to stop condition detection, no detection of ACK from master,
address mismatch)
<2> Ready flag
This flag indicates that data communication is enabled. Its function is the same as the INTIICAn
interrupt for ordinary data communication. This flag is set by interrupt servicing and cleared by the
main processing. Clear this flag by interrupt servicing when communication is started. However, the
ready flag is not set by interrupt servicing when the first data is transmitted. Therefore, the first data
is transmitted without the flag being cleared (an address match is interpreted as a request for the
next data).
<3> Communication direction flag
This flag indicates the direction of communication. Its value is the same as the TRCn bit.
Remark
n = 0, 1
IICA
Main processing
Interrupt servicing
INTIICAn
Flag
Setting
Data
Setting
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