4570 Datasheet, PDF (27/69 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
4570 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
CARRIER WAVE GENERATING CIRCUIT
The 4570 Group has a carrier wave generating circuit that
generates the transfer waveform for various remote control carrier
wave.
The carrier wave generating circuit outputs the signal inverted
every timer 3 underflow (CARRY) from port CARR.
When using the carrier wave generating circuit, select the f(XIN)
or f(XIN)/2 for the timer 3 count source (W31=“1”, W30=“0”).
When the bit 3 of the clock control register MR is “0” (system
clock=f(XIN)), f(XIN) is selected as the count source.
When the bit 3 of the clock control register MR is “1” (system
clock=f(XIN)/4), f(XIN)/2 is selected as the count source.
Set the count value corresponding to “L” interval of carrier wave
output to timer 3 reload register R3L.
Set the count value corresponding to “H” interval of carrier wave
output to timer 3 reload register R3H.
Also, timer 1 can auto-control the carrier wave output of port
CARR by setting the carrier wave output control register (C2).
When timer 3 is stopped, the output level of port CARR is
initialized. (“L” level)
The carrier wave is output from port CARR until the first timer
3 underflow occurs. The output of the carrier wave from port
CARR is disabled and the next count value is loaded from
reload register R1 to timer 1 by the first timer 1 underflow.
Then, the output of carrier wave is disabled until the second
timer 1 underflow occurs. Also, the next enable interval of
the carrier wave output can be set by setting the third count
value to timer 1 reload register R1 before the second timer 1
underflow occurs.
If the carrier wave output auto-control function is invalidated
(C20=“0”) while the carrier wave output is auto-controlled, the
output of port CARR retains the state when the auto-control
is invalidated regardless of timer 1 underflow. This state can
be terminated by timer 1 stop (W10=“0”).
When the carrier wave output auto-control function is validated
(C20=“1”) again after it is invalidated (C20=“0”), the auto-
control of carrier wave output is started again when the next
timer 1 underflow occurs.
Stop the timer 3 and invalidate the auto-control function by
timer 1 to use the port CARR output contorl bit (C21).
(1) Carrier wave output control register (C2)
Timer 1 can auto-control the output enable interval and the
output disable interval of the carrier wave output from port
CARR by setting the bit 0 of register C2 to “1.” Set the
contents of this register through register A with the TC2A
instruction.
The setting of the output enable/disable interval is described
below.
ΠValidate the carrier wave output auto-control function
(C20=“1”).
 Set the count value (“L” interval of carrier wave output) to
timer 3 and reload register R3L.
Ž Set the count value (“H” interval of carrier wave output) to
timer 3 reload register R3H.
 Set the count value (the output enable interval of carrier
wave from port CARR) to timer 1.
 Select the carrier wave (W11 = “1”) as the timer 1 count
source.
‘ Operate timer 1 (W10=“1”).
’ Operate timer 3 (W33=“1”).
“ Set the next count value (the output disable interval of
carrier wave from port CARR) to reload register R1 before
timer 1 underflow occurs.
(2) Notes when using the carrier wave output auto-control function
q Set the timer 1 and register C2 before timer 3 is started to
operate (W33=“1”).
q Stop the timer 1 (W10=“0”) after stopping the timer 3
(W33=“0”) while the carrier wave output is disabled in order
to stop the carrier wave output auto-control operation.
q If the carrier wave output auto-control function is invalidated
(C20=“0”) while the carrier wave output is auto-controlled,
the output of port CARR retains the state when the auto-
control is invalidated regardless of timer 1 underflow.
When the carrier wave output auto-control function is
validated (C20=“1”) again after it is invalidated (C20=“0”),
the auto-control by timer 1 is validated again when the next
timer 1 underflow occurs.
However, when the carrier wave output auto-control bit (C20)
is changed during timer 1 underflow, the error-operation may
occur.
q When the carrier wave output auto-control function is
selected, use the carrier wave CARRY as the timer 1 count
source.
If the ORCLK is used as the count source, a short pulse
may occur in port CARR output because ORCLK is not
synchronized with the carrier wave.
q When the carrier wave output auto-control function is
selected and data is set to reload register R1 while timer 1
is operating, avoid the timing that the contents of timer 1
becomes “0” to execute the T1AB instruction.
Table 11 Carrier wave output control register
Carrier wave output control register C2
at reset : 002
at RAM back-up : 002
W
C21 Port CARR output control bit
C20 Carrier wave output auto-control bit
Note: “W” represents write enabled.
0 Port CARR “L” level output
1 Port CARR “H” level output
0 ^{Auto-control output by timer 1 is invalid}
1 ^{Auto-control output by timer 1 is valid}
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