M16C6K9 Datasheet, PDF (175/292 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6K9 Group
Serial Interrupt Output
(2) The operation of serial interrupt
A cycle operation of serial interrupt starts with start frame and finishes with stop frame. There are
2 kinds of operation mode: continuous mode and quiet mode. The next operation mode is judged
by monitoring the length of stop frame sent from host side.
q The timing of serial interrupt cycle
Fig.SI-8 shows an example of basic timing of serial interrupt cycle.
➀ Start frame
The start frame will be detected if the SERIRQ remains “L” in 4-8 clock cycles.
➁IRQ data frame
Each IRQ data frame is 3 clock cycles.
•Channel 0-2,4:If the IRQ request bit is “0”, then the SERIRQ is driven to “L” during the 1^st clock
cycle of the corresponding data frame, to “H” during the 2^nd clock cycle, to high impedance during
the 3^rd clock cycle. If the IRQ request bit is “1”, then the SERIRQ is high impedance during all of
the 3 clock cycles.
•Channel 3:If the IRQ request bit is “0”, then the SERIRQ is high impedance during all of the 3
clock cycles. If the IRQ request bit is “1”, then the SERIRQ is driven to “L” during the 1^st clock
cycle of the corresponding data frame, to “H” during the 2^nd clock cycle, to high impedance during
the 3^rd clock cycle.
zStop frame
The stop frame will be detected if the SERIRQ remains “L” in 2 or 3 clock cycles. The next opera-
tion mode is quiet mode if the length of “L” is 2 clock cycles, the continuous mode if the length is
3 clock cycles.
Clock
SERIRQ
Driver source
Start frame
System side
frame 0
frame 1
frame 15
IOCHK
Stop frame
to the next cycle
Device side
Device side
System side
Fig.SI-8 Basic timing of serial interrupt cycle
Rev.1.00 Jun 06, 2003 page 175 of 290