RL78/G13 CHAPTER 13 SERIAL INTERFACE IICA
R01UH0146EJ0100 Rev.1.00 733
Sep 22, 2011
13.5.13 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 00 (IICCTL00) 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 the WUP0 bit 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 WUP0 bit after this interrupt
has been generated.
Figure 13-22 shows the flow for setting WUP0 = 1 and Figure 13-23 shows the flow for setting WUP0 = 0 upon an
address match.
Figure 13-22. Flow When Setting WUP0 = 1
Waits for 3 clocks.
Yes
No
START
WUP0 = 1
Wait
STOP instruction execution
MSTS0 = STD0 = EXC0 = COI0 =0?
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