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SDA fixed low, R8C master I2C bus interface

Latest Updated:10/06/2016

Question:

When carrying out I2C communication using the I2C bus interface of an R8C device on the master side, sometimes the SDA line is fixed to low level and communication can't be carried out.
How do I resolve this situation?

Answer:

A clock discrepancy may occur between the master and slave due to noise, etc. on the SCL line of the I2C bus. This occurs due to differences in VIH/VIL characteristics or noise elimination capabilities of the two devices causing a difference in whether or not noise, etc. on the SCL line is recognized is a clock.

Please carry out steps 1-3 below for the R8C device on the master side.
1. Set the IICRST bit of the ICCR2 register to 1 (release SCL/SDA output latch of this station).
2. Set the IICRST bit of ICCR2 register to 0 (release internal reset).
3. Check the input level of SCL/SDA (check port input of shared pin).

Depending on the result of 3 above, perform a or b.

a) If SDA and SCL are high level
     SDA/SCL of the R8C device on the master side may be fixed  to low level. Please carry out step 4 onwards of the procedure shown in FAQNo:107183 .

b) If SDA is low level
     SDA of the slave side may be fixed to low level. Please refer to FAQNo:107457 for how to resolve SDA on the slave side being fixed to low level.

Suitable Products
R8C/32C
R8C/33C
R8C/34C
R8C/35C
R8C/36C
R8C/38C
R8C/3GC
R8C/3JC
R8C/32M
R8C/33M
R8C/34M
R8C/35M
R8C/36M
R8C/38M
R8C/3GM
R8C/3JM
R8C/3MK
R8C/34K
R8C/3MU
R8C/34U
R8C/3MQ
R8C/L35C
R8C/L36C
R8C/L38C
R8C/L3AC
R8C/L35M
R8C/L36M
R8C/L38M
R8C/L3AM
R8C/LA3A
R8C/LA5A
R8C/LA6A
R8C/LA8A
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