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16.13 Communication Reservation
16.13.1 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 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).
A communication is automatically started as the master by setting the IICC0.SPIE0 bit to 1, detecting the bus
<R>
release due to an interrupt request (INTIIC0) occurrence (detecting a stop condition), and then writing the address to
the IIC0 register. Before detecting a stop condition, data written to the IIC0 register is set to invalid.
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 16-6. These wait periods can be set via the
settings for the IICX0.CLX0, IICCL0.SMC0, IICCL0.CL01, and IICCL0.CL00 bits.
<R>
CLX0
SMC0
CL01
0
0
0
0
0
0
0
0
1
0
0
1
0
1
0
0
1
1
0
1
1
1
1
0
1
1
1
2
CHAPTER 16 I
C BUS
Table 16-6. Wait Periods
CL00
Selected Clock
0
f
/2
XX
1
f
/2
XX
0
f
XX
1
f
/3
XX
1/0
f
/2
XX
0
f
XX
1
f
/3
XX
1/0
f
/2
XX
0
f
XX
User's Manual U16896EJ2V0UD
Wait Period
46 clocks
86 clocks
43 clocks
102 clocks
30 clocks
15 clocks
36 clocks
18 clocks
9 clocks
511
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