Arbitration-Lost Detection Functions; Master Arbitration-Lost Detection (Male Bit) - Renesas RX100 Series User Manual

RX13T Group
24.9

Arbitration-Lost Detection Functions

In addition to the normal arbitration-lost detection function defined by the I
to prevent double-issue of a start condition, to detect arbitration-lost during transmission of NACK, and to detect
arbitration-lost in slave transmit mode.
24.9.1

Master Arbitration-Lost Detection (MALE Bit)

The RIIC drives the SDA0 line low to issue a start condition. However, if the SDA0 line has already been driven low by
another master device issuing a start condition, the RIIC causes arbitration to be lost, so priority is given to transfer by
the other master device. Similarly, if the ICCR2.ST bit is set to 1 while the ICCR2.BBSY flag is 1 (bus busy state),
arbitration is lost, so priority is given to transfer by the other master device. No start condition is issued in this case.
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 SDA0 line do not match (the high output as the internal SDA output; i.e. the SDA0 pin
is in the high-impedance state) and the low level is detected on the SDA0 line, the RIIC loses in arbitration.
After a loss in arbitration of mastership, the RIIC immediately enters slave receive 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 ICFER.MALE bit is 1
(master arbitration-lost detection enabled).
Conditions for master arbitration-lost
 Non-matching of the internal level for output on SDA and the level on the SDA0 line after a start condition was
issued by setting the ICCR2.ST bit to 1 while the ICCR2.BBSY flag was set to 0 (erroneous issuing of a start
condition)
 Setting of the ICCR2.ST bit 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 SDA0
line in master transmit mode (bits MST and TRS in the ICCR2 register = 11b)
R01UH0822EJ0100 Rev.1.00
Jul 31, 2019
2
24. I C-bus Interface (RIICa)
2
C-bus specification, the RIIC has functions
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