3819 Datasheet, PDF (41/61 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3819 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
INTERRUPT INTERVAL DETERMINATION
FUNCTION
The 3819 group builds in an interrupt interval determination circuit.
This interrupt interval determination circuit has an 8-bit binary up
counter. Using this counter, it determines a duration of time from
the rising transition (falling transition) of an input signal pulse on
the P42/INT2 pin to the rising transition (falling transition) of the
signal pulse that is input next.
How to determine the interrupt interval is described below.
ŒEnable the INT2 interrupt by setting the bit 2 of the interrupt con-
trol register 1 (address 003E16). Select the rising interval or
falling interval by setting the bit 2 of the interrupt edge selection
register (address 003A16).
 Set the bit 0 of the interrupt interval determination control regis-
ter (address 003116) to “1” (interrupt interval determination
operating).
ŽSelect the sampling clock of 8-bit binary up counter by setting
the bit 1 of the interrupt interval determination control register.
When writing “0”, f(XIN)/256 is selected (the sampling interval:
32 µs at f(XIN) = 8.38 MHz) ; when “1”, f(XIN)/512 is selected (the
sampling interval: 64 µs at f(XIN) = 8.38 MHz).
 When the signal of polarity which is set on the INT2 pin (rising or
falling transition) is input, the 8-bit binary up counter starts
counting up of the selected counter sampling clock.
When the signal of polarity above  is input again, the value of
the 8-bit binary up counter is transferred to the interrupt interval
determination register (address 003016), and the remote control
interrupt request occurs. Immediately after that, the 8-bit binary
up counter is cleared to “0016”. The 8-bit binary up counter con-
tinues to count up again from “0016”.
‘When count value reaches “FF16”, the 8-bit binary up counter
stops counting up. Then, simultaneously when the next counter
sampling clock is input, the counter sets value “FF16” to the in-
terrupt interval determination register to generate the counter
overflow interrupt request.
Noise filter
The P42/INT2 pin builds in the noise filter.
The noise filter operation is described below.
ŒSelect the sampling clock of the input signal with the bits 2 and
3 of the interrupt interval determination control register. When
not using the noise filter, set “002”.
The P42/INT2 input signal is sampled in synchronization with the
selected clock. When sampling the same level signal in series,
the signal is recognized as the interrupt signal, and the interrupt
request occurs.
When setting the bit 4 of interrupt interval determination control
register to “1”, the interrupt request can occur at both rising and
falling edges.
When using the noise filter, set the minimum pulse width of the
INT2 input signal to 2 cycles or more.
Note : In the low-speed mode (CM7=1), the interrupt interval determination
function can not operate.
The counter
sampling clock
selection bit
f(XIN)/256
f(XIN)/512
8-bit binary up counter
INT2 interrupt input
Noise filter
One-sided/both-sided
Noise filter sampling
detection selection bit
clock selection bit
1/256
1/64 ^1/128
Divider
Interrupt interval
determination register
address 003016
Data bus
The counter overflow
interrupt request or
remote control interrupt request
f(XIN)
Fig. DE-1 Block diagram of interrupt interval datermination circuit
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