
CHAPTER 19 I
2
C BUS
User’s Manual U16890EJ1V0UD
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19.13 Communication Reservation
19.13.1 When communication reservation function is enabled (IICF0.IICRSV0 bit = 0)
To start master device communications when not currently using a bus, a communication reservation can be made
to enable transmission of a start condition when the bus is released. There are two modes under which the bus is not
used.
When arbitration results in neither master nor slave operation
When an extension code is received and slave operation is disabled (ACK signal is not returned and the bus was
released when the IICC0.LREL0 bit was set to “1”).
If the IICC0.STT0 bit is set (1) while the bus is not used, a start condition is automatically generated and wait status
is set after the bus is released (after a stop condition is detected).
When the bus release is detected (when a stop condition is detected), writing to the IIC0 register causes the
master’s address transfer to start. At this point, the IICC0.SPIE0 bit should be set (1).
When the STT0 bit has been set (1), the operation mode (as start condition or as communication reservation) is
determined according to the bus status.
If the bus has been released..............................................a start condition is generated
If the bus has not been released (standby mode)..............communication reservation
To detect which operation mode has been determined for the STT0 bit, set the STT0 bit (1), wait for the wait period,
then check the IICS0.MSTS0 bit.
Wait periods, which should be set via software, are listed in Table 19-6. These wait periods can be set via the
settings for the IICCL0.SMC0, IICCL0.CL01, and IICCL0.CL00 bits.
Table 19-6. Wait Periods
SMC0
CL01
CL00
Wait Period
0
0
0
26 clocks
0
0
1
46 clocks
0
1
0
92 clocks
0
1
1
37 clocks
1
0
0
1
0
1
16 clocks
1
1
0
32 clocks
1
1
1
13 clocks