4518 Datasheet, PDF (36/160 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4518 Group
(1) Timer control registers
• Timer control register PA
Register PA controls the count operation of prescaler. Set the
contents of this register through register A with the TPAA instruc-
tion.
• Timer control register W1
Register W1 controls the selection of timer 1 count auto-stop cir-
cuit, and the count operation and count source of timer 1. Set the
contents of this register through register A with the TW1A instruc-
tion. The TAW1 instruction can be used to transfer the contents
of register W1 to register A.
• Timer control register W2
Register W2 controls the selection of CNTR0 output, and the
count operation and count source of timer 2. 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.
• Timer control register W3
Register W3 controls the selection of the count operation and
count source of timer 3 count auto-stop circuit. 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.
• Timer control register W4
Register W4 controls the D7/CNTR1 output, the expansion of “H”
interval of PWM output, and the count operation and count
source of timer 4. Set the contents of this register through regis-
ter A with the TW4A instruction. The TAW4 instruction can be
used to transfer the contents of register W4 to register A.
• Timer control register W5
Register W5 controls the period measurement circuit and target
signal for period measurement. Set the contents of this register
through register A with the TW5A instruction. The TAW5 instruc-
tion can be used to transfer the contents of register W5 to
register A.
• Timer control register W6
Register W6 controls the count edges of CNTR0 pin and CNTR1
pin, selection of CNTR1 output auto-control circuit and the D6/
CNTR0 pin function. Set the contents of this register through reg-
ister A with the TW6A instruction. The TAW6 instruction can be
used to transfer the contents of register W6 to register A..
(2) Prescaler
Prescaler is an 8-bit binary down counter with the prescaler reload
register PRS. Data can be set simultaneously in prescaler and the
reload register RPS with the TPSAB instruction. Data can be read
from reload register RPS with the TABPS instruction.
Stop counting and then execute the TPSAB or TABPS instruction
to read or set prescaler data.
Prescaler starts counting after the following process;
➀ set data in prescaler, and
➁ set the bit 0 of register PA to “1.”
When a value set in reload register RPS is n, prescaler divides the
count source signal by n + 1 (n = 0 to 255).
Count source for prescaler is the instruction clock (INSTCK).
Once count is started, when prescaler underflows (the next count
pulse is input after the contents of prescaler becomes “0”), new
data is loaded from reload register RPS, and count continues
(auto-reload function).
The output signal (ORCLK) of prescaler can be used for timer 1, 2,
3, and 4 count sources.
(3) Timer 1 (interrupt function)
Timer 1 is an 8-bit binary down counter with the timer 1 reload reg-
ister (R1). Data can be set simultaneously in timer 1 and the reload
register (R1) with the T1AB instruction. Data can be written to re-
load register (R1) with the TR1AB instruction. Data can be read
from timer 1 with the TAB1 instruction.
Stop counting and then execute the T1AB or TAB1 instruction to
read or set timer 1 data.
When executing the TR1AB instruction to set data to reload regis-
ter R1 while timer 1 is operating, avoid a timing when timer 1
underflows.
Timer 1 starts counting after the following process;
➀ set data in timer 1
➁ set count source by bits 0 and 1 of register W1, and
➂ set the bit 2 of register W1 to “1.”
When a value set in reload register R1 is n, timer 1 divides the
count source signal by n + 1 (n = 0 to 255).
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).
INT0 pin input can be used as the start trigger for timer 1 count op-
eration by setting the bit 0 of register I1 to “1.”
Also, in this time, the auto-stop function by timer 1 underflow can
be performed by setting the bit 3 of register W1 to “1.”
Timer 1 underflow signal divided by 2 can be output from CNTR0
pin by clearing bit 3 of register W2 to “0” and setting bit 0 of regis-
ter W6 to “1”.
The period measurement circuit starts operating by setting bit 2 of
register W5 to “1” and timer 1 is used to count the one-period of the
target signal for the period measurement. In this time, the timer 1
interrupt request flag (T1F) is not set by the timer 1 underflow sig-
nal, it is the flag for detecting the completion of period
measurement.
Rev.3.01 2005.06.15 page 36 of 157
REJ03B0008-0301