Datasheet

V850ES/JG3 CHAPTER 17 I
2
C BUS
R01UH0015EJ0300 Rev.3.00 Page 591 of 870
Sep 30, 2010
17.14 Communication Reservation
17.14.1 When communication reservation function is enabled (IICFn.IICRSVn bit = 0)
To start master device communications when not currently using the bus, a communication reservation can be made to
enable transmission of a start condition when the bus is released. There are two modes in 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 IICCn.LRELn bit was set to 1) (n = 0 to 2).
If the IICCn.STTn bit is set to 1 while the bus is not used, a start condition is automatically generated and a wait state 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 IICn register causes master
address transfer to start. At this point, the IICCn.SPIEn bit should be set to 1 (n = 0 to 2).
When STTn has been set to 1, the operation mode (as start condition or as communication reservation) is determined
according to the bus status (n = 0 to 2).
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 STTn bit, set the STTn bit to 1, wait for the wait period,
then check the IICSn.MSTSn bit (n = 0 to 2).
The wait periods, which should be set via software, are listed in Table 17-6. These wait periods can be set by the SMCn,
CLn1, and CLn0 bits of the IICCLn register and the IICXn.CLXn bit (n = 0 to 2).