MITSUBISHI MICROCOMPUTERS
M37207MF-XXXSP/FP, M37207M8-XXXSP
M37207EFSP/FP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
and ON-SCREEN DISPLAY CONTROLLER
72
INTERRUPT INTERVAL DETERMINATION
FUNCTION
This microcomputer incorporates an interrupt interval determination
circuit. This interrupt interval determination circuit has an 8-bit binary
up counter as shown in Figure 69. Using this counter, it determines
an interval on the INT1 or INT2 (refer to Figure 72).
The following describes how the interrupt interval is determined.
1. The interrupt input to be determined (INT1 input or INT2 input) is
selected by using bit 2 in the interrupt interval determination con-
trol register (address 00D816). When this bit is cleared to “0,” the
INT1 input is selected ; when the bit is set to “1,” the INT2 input is
selected.
2. When the INT1 input is to be determined, the polarity is selected
by using bit 3 of the interrupt interval determination control
register ; when the INT2 input is to be determined, the polarity is
selected by using bit 4 of the interrupt interval determination
control register.
When the relevant bit is cleared to “0,” determination is made of
the interval of a positive polarity (rising transition) ; when the bit is
set to “1,” determination is made of the interval of a negative po-
larity (falling transition).
3. The reference clock is selected by using bit 1 of the interrupt inter-
val determination control register. When the bit is cleared to “0,” a
32 ms clock is selected ; when the bit is set to “1,” a 16 ms clock is
selected (based on an oscillation frequency of 8MHz in either
case).
4. Simultaneously when the input pulse of the specified polarity
(rising or falling transition) occurs on the INT1 pin (or INT2 pin),
the 8-bit binary up counter starts counting up with the selected
reference clock (32 ms or 16 ms).
5. Simultaneously with the next input pulse, the value of the 8-bit
binary up counter is loaded into the interrupt interval determina-
tion register (address 00D716) and the counter is immediately re-
set (“0016”). The reference clock is input in succession even after
the counter is reset, and the counter restarts counting up from
“0016.”
6. When count value “FE16” is reached, the 8-bit binary up counter
stops counting. Then, simultaneously when the next reference
clock is input, the counter sets value “FF16” to the interrupt inter-
val determination register. The reference clock is generated by
setting bit 0 of PWM mode register 1 to “0.”
Fig. 69. Block Diagram of Interrupt Interval Determination Circuit
8
Data bus
Control
circuit
Connected to
black colored
side at rest.
Selection gate :
(Address 00D7
16
)
32µs
RE1
16µs
8-bit binary up counter (8)
Interrupt interval determination register (8)
RE0
8
INT1 (Note)
RE2
INT2 (Note)
Note: The pulse width of external interrupt INT1 and INT2 needs 5 or more machine cycles.
RE : Interrupt interval determination control register
