Datasheet

78K0/Ix2 CHAPTER 15 SERIAL INTERFACE IICA
R01UH0010EJ0500 Rev.5.00 505
Feb 28, 2012
15.5.13 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 the 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 15-23 shows the flow for setting WUP = 1 and Figure 15-24 shows the flow for setting WUP = 0 upon an
address match.
Figure 15-23. Flow When Setting WUP = 1
Waits for 3 clock
s.
Yes
No
START
WUP = 1
Wait
STOP instruction execution
MSTS0 = STD0 = EXC0 = COI0 =0?