4570 Datasheet, PDF (24/69 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
4570 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
(1) Timer control registers
q Timer control register W1
Register W1 controls the count source and count operation
of timer 1, the frequency dividing ratio and count operation
of prescaler. Set the contents of this register through
register A with the TW1A instruction. The TAW1 instruction
can be used to transfer the contents of register W1 to
register A.
q Timer control register W2
Register W2 controls the count operation and count source
of timer 2 and D9/TOUT pin function. Set the contents of
this register through register A with the TW2A instruction.
The TAW2 instruction can be used to transfer the contents
of register W2 to register A.
q Timer control register W3
Register W3 controls the count operation and count source
of timer 3. Set the contents of this register through register
A with the TW3A instruction. The TAW3 instruction can
be used to transfer the contents of register W3 to register
A.
q Timer count value store register W5
2-bit register. The contents of the high-order 2 bits (bits 9
and 8) of the 10-bit ROM pattern at address in page p
specified by registers D and A is stored in this register
W5 with the TABP p instruction.
In addition, data can be transferred between the low-order
2 bits of register A and this register W5 with the TW5A or
TAW5 instruction. Data can be read/written to/from the
high-order 2 bits of timer 1 with the T1AB or TAB1
instruction.
(2) Precautions
Note the following for the use of timers.
q Prescaler
Stop the prescaler operation to change its frequency
dividing ratio.
q Count source
Stop timer 1, 2 or 3 counting to change its count source.
q Reading the timer count value
Stop each of the timers and then execute the TAB1, TAB2
or TAB3 instruction to read timer 1, 2 or 3 data.
q Writing to reload register R1
When writing data to reload register R1 while timer 1 is
operating, avoid a timing when timer 1 underflows.
q Writing to reload register R3H
When writing data to reload register R3H while timer 3 is
operating, avoid a timing when timer 3 underflows.
(3) Prescaler
Prescaler is a frequency divider. Its frequency dividing ratio
can be selected. The count source of prescaler is the
instruction clock.
Use the bit 2 of register W1 to select the prescaler dividing
ratio and the bit 3 to start and stop its operation. When the bit
3 of register W1 is cleared to “0,” prescaler is initialized, and
the output signal (ORCLK) stops.
(4) Timer 1 (interrupt function)
Timer 1 is a 10-bit binary down counter with the timer 1 reload
register (R1). The 10-bit data can be set in timer 1 through
registers A, B and W5. Set bits 0 to 3 to register A, bits 4 to
7 to regiser B and bits 8 to 9 to register W5 to set data to
timer 1. Also, ROM pattern (bits 0 to 9) can be set to registers
A, B and W5 with the TABP p instruction. Execute the T1AB
instruction to set data in timer 1.
When timer 1 stops, 10-bit data can be set simultaneously in
timer 1 and the reload register (R1) with the T1AB instruction.
When timer 1 is operating, data can be set only in the reload
register (R1) with the T1AB instruction.
When setting the next count data to reload register R1 while
timer 1 is operating, be sure to set data before timer 1
underflows.
Timer 1 starts counting after the following process;
Πset data in timer 1,
 select the count source with bit 1 of register W1,
Ž set the bit 0 of register W1 to “1.”
Once count is started, when timer 1 underflows (the next
count pulse is input after the contents of timer 1 becomes
“0”), the timer 1 interrupt request flag (T1F) is set to “1,” new
data is loaded from reload register R1, and count continues
(auto-reload function).
When a value set in reload register R1 is n, timer 1 divides
the count source signal by n + 1 (n = 0 to 1023).
Data can be read from timer 1 to registers A, B and W5.
Stop counting and then execute the TAB1 instruction to read
its data.
(5) Timer 2 (interrupt function)
Timer 2 is an 8-bit binary counter with the timer 2 reload
register (R2). Data can be set simultaneously in timer 2 and
the reload register (R2) with the TAB2 instrucion. Also, data
can be set only in the reload register (R2) with the TR2AB
instruction.
Timer 2 starts counting after following process;
Πset data in timer 2,
 select the count source with bits 0 and 1 of register W2,
Ž set the bit 3 of register W2 to “1.”
Once count is started, when timer 2 underflows (the next
count pulse is input after the contents of timer 2 becomes
“0”), the timer 2 interrupt request flag (T2F) is set to “1,” new
data is loaded from reload register R2, and count continues
(auto-reload function).
When a value set in reload register R2 is n, timer 2 divides
the count source signal by n+1 (n = 0 to 255).
Data can be read from timer 2 to registers A and B with the
TAB2 instruction. Stop counting and then execute the TAB2
instruction to read its data.
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