17.4.10 First Kclk Falling Interrupt; Figure 17.15 Timing Of First Kclk Interrupt - Renesas H8S Series Hardware Manual

Section 17 Keyboard Buffer Control Unit (KBU)

17.4.10 First KCLK Falling Interrupt

An interrupt can be generated by detecting the first falling edge of KCLK on reception and
transmission. Software standby, watch, and subsleep modes can be cancelled by a first KCLK
falling interrupt.
• Reception
When both KBIOE and KBE are set to 1, KCIF is set after the first falling edge of KCLK has
been detected.
At this time, if KCIE is set to 1, the CPU is requested an interrupt.
KCIF is set at the same time when the RXCR3 to RXCR0 bits in KBCRL are incremented
from B'0000 to B'0001.
• Transmission
When both KBIOE and KBTS are set to 1, the KCIF is set after the first falling edge of KCLK
has been detected.
At this time, if KCIE is set to 1, the CPU is requested an interrupt.
KCIF is set at the same time when the TXCR3 to TXCR0 bits in KBCR2 are incremented from
B'0000 to B'0001.
• Determining interrupt generation
By checking the KBE, KBTS, and KBTE bits, it can be determined whether the first KCLK
falling interrupt is occurred during reception or transmission.
During reception: KBE = 1
During transmission: KBTS = 1 or KBTE = 1 (Check KBTE = 1 because the KBTS is
automatically cleared after transfer has been completed.)
1
KCLK
KD
Start bit
RXCR3
0000
to RXCR0
Interrupt
internal
signal
Interrupt generated
Rev. 3.00 Jul. 14, 2005 Page 606 of 986
REJ09B0098-0300
2 3
0 1
0001 0010
(a) Reception

Figure 17.15 Timing of First KCLK Interrupt

I/O inhibit
KCLK
KD
Start bit
TXCR3
0000
to TXCR0
Interrupt
internal
signal
Interrupt generated
(b) Transmission
1 2
0 1
0001 0010