Renesas H8S Series Hardware Manual page 655

• Canceling software standby mode, watch mode, and subsleep mode
Software standby, watch, and subsleep modes are cancelled by a first KCLK falling interrupt.
In this case, an interrupt is generated at the first KCLK since software standby mode, watch
mode, or subsleep mode has been shifted (figure 17.17).
Notes on canceling operation are explained below.
 When a transition to software standby mode, watch mode, or subsleep mode is performed
while both KBIOE and KCIE are set to 1, canceling the current mode is enabled by an first
KCLK falling interrupt (the KBE and KBTS are not affected).
 When software standby mode, watch mode, and subsleep mode are cancelled by a first
KCLK falling interrupt, the KCIF flag is not set (only the internal flag is set).
In the first KCLK interrupt handling routine, the KCIF bit is checked. If the KCIF is 0, it
indicates that the interrupt is generated after software standby mode, watch mode, and
subsleep mode have been cancelled.
 When software standby mode, watch mode, or subsllep mode is cancelled by receiving a
receive clock, the reception is ignored. Execute reception terminating processing by an
interrupt handing routine, and then request retransfer.
 When transition to software standby mode, watch mode, or subsleep mode and canceling
the mode by a first KCLK falling interrupt are performed during data transmission, state
before performing mode transition is held immediately after canceling the mode.
Therefore, initialization by an interrupt handling routine is required. Precautions as (b) and
(c) which are shown in figure 17.16 should be applied on interrupt generation.
 Priority of canceling software standby mode, watch mode, and subsleep mode are decided
by the setting of ICR.
 The interrupt signal path and flag setting of the first KCLK interrupt in normal operation
differ from those in software standby mode, watch mode, and subsleep mode. Figure 17.6
shows the interrupt signal paths of the first KCLK interrupt.
Signal A: Interrupt signal in normal operation
Signal B: Interrupt signal in software standby mode, watch made, and subsleep mode
 KCLK is input directly to the interrupt control block, not through the KBU, in software
standby mode, watch mode, and subsleep mode, and then an interrupt is generated by
detection of a falling edge. Therefore, the KCIF flag is not set. In this case, a flag that is in
the interrupt control block is set. The internal flag is automatically cleared after an interrupt
request is sent to the CPU. Figure 17.18 shows setting and clearing timing.
Section 17 Keyboard Buffer Control Unit (KBU)
Rev. 3.00 Jul. 14, 2005 Page 607 of 986
REJ09B0098-0300