Skip to main content
Knowledgebase
Home
Renesas Singapore - Knowledgebase

What could be caused IIC bus will switch to slave receive mode?

Latest Updated:03/19/2008

Question:

During master transmit/master receive operations, even though I'm transmitting with a single master, occasionally, the IIC bus will switch to slave receive mode, stopping transmission. What could be causing this?

Answer:

Even during single master transmission, sometimes data indiscrepancies cause loss of arbitration on the IIC bus line. This is especially likely to occur if there is noise, etc. affecting the SDA line. When arbitration is lost, depending on the noise waveform, the data indiscrepancy may be mistakenly recognized as a start or stop condition. Therefore, please plan IIC bus line wiring lengths and board layouts to minimize noise effects as well as prepare return processing and so on by software even for single master transmission. Note in particular that when loss of arbitration occurs during single master transmission, master rights will be lost regardless of bus free state (both SCL and SDA levels are high). In addition, for how to clear the bus busy flag (BBSY) when it has become 1 regardless of bus free state, refer to FAQ No.107070 or FAQ No.107073. The clearing condition differs by product.
Suitable Products
H8S/2643
H8S/2630, 2639, 2638, 2636, 2635
H8S/2633
H8S/2556, 2552, 2506
H8S/2472, 2463, 2462
H8S/2378, 2378R
H8S/2368
H8S/2268, 2264
H8S/2258, 2239, 2238, 2237, 2227
H8S/2199R
H8S/2168
H8S/2148, 2144
H8S/2140B
H8S/2138, 2134
H8S/2128, 2124
H8S/2117, 2117R
H8S/2116
H8S/2114R
H8S/2111B
H8S/2110B
H8SX/1668R, H8SX/1668M
H8SX/1663
H8SX/1658R, H8SX/1658M
H8SX/1653
H8SX/1648G, H8SX/1648H
H8SX/1648A, H8SX/1648L
H8SX/1638, H8SX/1638L
H8SX/1622
H8SX/1544