MITSUBISHI MICROCOMPUTERS
3822 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Timer X
ꢀReal time port control
Timer X is a 16-bit timer that can be selected in one of four modes
and can be controlled the timer X write and the real time port by
setting the timer X mode register.
While the real time port function is valid, data for the real time port
are output from ports P52 and P53 each time the timer X
underflows. (However, after rewriting a data for real time port, if
the real time port control bit is changed from “0” to “1”, data are
output independent of the timer X operation.) If the data for the
real time port is changed while the real time port function is valid,
the changed data are output at the next underflow of timer X.
Before using this function, set the corresponding port direction
registers to output mode.
(1) Timer Mode
The timer counts f(XIN)/16 (or f(XCIN)/16 in low-speed mode).
(2) Pulse Output Mode
Each time the timer underflows, a signal output from the CNTR0
pin is inverted. Except for this, the operation in pulse output mode
is the same as in timer mode. When using a timer in this mode,
set the corresponding port P54 direction register to output mode.
ꢀNote on CNTR0 interrupt active edge
selection
CNTR0 interrupt active edge depends on the CNTR0 active edge
(3) Event Counter Mode
switch bit.
The timer counts signals input through the CNTR0 pin.
Except for this, the operation in event counter mode is the same
as in timer mode. When using a timer in this mode, set the corre-
sponding port P54 direction register to input mode.
b7
b0
Timer X mode register
(TXM : address 002716
)
(4) Pulse Width Measurement Mode
The count source is f(XIN)/16 (or f(XCIN)/16 in low-speed mode). If
CNTR0 active edge switch bit is “0”, the timer counts while the in-
put signal of CNTR0 pin is at “H”. If it is “1”, the timer counts while
the input signal of CNTR0 pin is at “L”. When using a timer in this
mode, set the corresponding port P54 direction register to input
mode.
Timer X write control bit
0 : Write value in latch and counter
1 : Write value in latch only
Real time port control bit
0 : Real time port function invalid
1 : Real time port function valid
P5
2
data for real time port
data for real time port
P53
Timer X operating mode bits
b5 b4
0
0
1
1
0 : Timer mode
1 : Pulse output mode
0 : Event counter mode
1 : Pulse width measurement mode
ꢀTimer X write control
If the timer X write control bit is “0”, when the value is written in the
address of timer X, the value is loaded in the timer X and the latch
at the same time.
CNTR0 active edge switch bit
0 : Count at rising edge in event counter mode
Start from “H” output in pulse output mode
Measure “H” pulse width in pulse width
measurement mode
If the timer X write control bit is “1”, when the value is written in the
address of timer X, the value is loaded only in the latch. The value
in the latch is loaded in timer X after timer X underflows.
If the value is written in latch only, when writing in the timer latch at
the timer underflow, the value is set in the timer and the latch at
one time. Additionally, unexpected value may be set in the high-or-
der counter when the writing in high-order latch and the underflow
of timer X are performed at the same timing.
Falling edge active for CNTR0 interrupt
1 : Count at falling edge in event counter mode
Start from “L” output in pulse output mode
Measure “L” pulse width in pulse width
measurement mode
Rising edge active for CNTR
Timer X stop control bit
0 : Count start
0 interrupt
1 : Count stop
Fig. 22 Structure of timer X mode register
26
MITSUBISHI [ Mitsubishi Group ]
