CHAPTER 17 SERIAL INTERFACE IIC0
Preliminary User’s Manual U17260EJ3V1UD
439
Figure 17-22. Communication Reservation Protocol
DI
SET1 STT0
Define communication
reservation
Wait
MSTS0 = 0?
(Communication reservation)
Note
Yes
No
(Generate start condition)
Cancel communication
reservation
MOV IIC0, #
××
H
EI
Sets STT0 flag (communication reservation)
Defines that communication reservation is in effect
(defines and sets user flag to any part of RAM)
Secures wait period set by software (see
Table 18-6
).
Confirmation of communication reservation
Clear user flag
IIC0 write operation
Note
The communication reservation operation executes a write to IIC shift register 0 (IIC0) when a stop
condition interrupt request occurs.
Remark
STT0: Bit 1 of IIC control register 0 (IICC0)
MSTS0: Bit 7 of IIC status register 0 (IICS0)
IIC0:
IIC shift register 0
(2) When communication reservation function is disabled (bit 0 (IICRSV) of IIC flag register 0 (IICF0) = 1)
When bit 1 (STT0) of IIC control register 0 (IICC0) is set to 1 when the bus is not used in a communication
during bus communication, this request is rejected and a start condition is not generated. The following two
statuses are included in the status where 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 bit 6 (LREL0) of IICC0 was set to 1)
To confirm whether the start condition was generated or request was rejected, check STCF (bit 7 of IICF0).
The time shown in Table 17-7 is required until STCF is set to 1 after setting STT0 = 1. Therefore, secure the
time by software.
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