RX610 Group
22. I
2
C Bus Interface (RIIC)
R01UH0032EJ0120 Rev.1.20
Page 757 of 1006
Feb 20, 2013
22.9
Arbitration-Lost Detection Functions
In addition to the normal arbitration-lost detection function defined by the I
2
C bus standard, the RIIC has functions to
prevent double-issue of a start condition, to detect arbitration during transmission of NACK, and to detect arbitration in
slave transmit mode.
22.9.1
Master Arbitration Lost Detection (MALE Bit)
The RIIC drives the SDAn line low to issue a start condition. However, if the SDAn line has already been driven low by
another master device issuing a start condition, the RIIC regards its own issuing of a start condition as an error and
considers this a loss in arbitration, so priority is given to transfer by the other master device. Similarly, if a request to
issue a start condition is made by setting the ST bit in ICCR2 to 1 while the bus is busy (BBSY flag = 1 in ICCR2), the
RIIC regards this as a double-issuing-of-start-condition error and considers itself to have lost in arbitration, thus
preventing a failure of transfer due to issuing of a start condition while transfer is in progress.
When a start condition is issued successfully, if the data for transmission including the address bits (i.e. the internal SDA
output level) and the level on the SDAn line do not match (the high output as the internal SDA output; i.e. the SDAn pin
is in the high-impedance state) and the low level is detected on the SDAn line, the RIIC loses in arbitration.
After a loss in arbitration of mastership, the RIIC immediately enters slave receiver mode. If a slave address (including
the general call address) matches its own address at this time, the RIIC continues in slave operation.
A loss in arbitration of mastership is detected when the following conditions are met while the MALE bit in ICFER is 1
(master arbitration lost detection enabled).
[Master arbitration lost conditions]
•
Non-matching of the internal level for output on SDA and the level on the SDAn line after a start condition was
issued by setting the ST bit in ICCR2 to 1 while the BBSY flag in ICCR2 was cleared to 0 (erroneous issuing of a
start condition)
•
Setting of the ST bit in ICCR2 to 1 (start condition double-issue error) while the BBSY flag is set to 1
•
When the transmit data excluding acknowledge (internal SDA output level) does not match the level on the SDAn
line in master transmit mode (MST and TRS bits = 11b in ICCR2)
Summary of Contents for RX600 Series
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