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CHAPTER 16 SERIAL INTERFACE IICA
User’s Manual U19780EJ2V0UD
456
16.5.13 Wakeup function
The I
2
C bus slave function is a function that generates an interrupt request signal (INTIICA0) when a local address
and extension code have been received.
This function makes processing more efficient by preventing unnecessary INTIICA0 signal from occurring when
addresses do not match.
When a start condition is detected, wakeup standby mode is set. This wakeup standby mode is in effect while
addresses are transmitted due to the possibility that an arbitration loss may change the master device (which has
generated a start condition) to a slave device.
However, when a stop condition is detected, bit 4 (SPIE0) of IICA control register 0 (IICACTL0) is set regardless of
the wakeup function, and this determines whether interrupt requests are enabled or disabled.
To use the wakeup function in the STOP mode, set WUP to 1. Addresses can be received regardless of the
operation clock. An interrupt request signal (INTIICA0) is also generated when a local address and extension code
have been received. Operation returns to normal operation by using an instruction to clear (0) the WUP bit after this
interrupt has been generated.
Figure 16-21 shows the flow for setting WUP and Figure 16-22 shows the flow for clear WUP = 0 upon an address
match.
Figure 16-21. Flow When Setting WUP = 1
Waits for 3 clocks.
Yes
No
START
WUP = 1
Wait
STOP instruction execution
MSTS0 = STD0 = EXC0 = COI0 =0?