Precautions - Epson S1C88655 Technical Manual

13.10 Precautions

(1) The programmable timer actually enters into
RUN or STOP status at the falling edge of the
input clock after writing to the PTRUNx
register. Consequently, when "0" is written to
PTRUNx, the timer stops after counting once
more (+1). PTRUNx is read as "1" until the
timer actually stops.
Figure 13.10.1 shows the timing chart at the
RUN/STOP control.
Input clock
PTRUNx(RD)
PTRUNx(WR)
PTMx 42H
Fig. 13.10.1 Timing chart at RUN/STOP control
(2) When the SLP instruction is executed while the
programmable timer is running (PTRUNx =
"1"), the timer stops counting during SLEEP
status. When SLEEP status is canceled, the
timer starts counting. However, the operation
becomes unstable immediately after SLEEP
status is canceled. Therefore, when shifting to
SLEEP status, stop the 16-bit programmable
timer (PTRUNx = "0") prior to executing the
SLP instruction.
Same as above, the TOUT signal output should
be disabled (PTOUTx = "0") so that an unstable
clock is not output to the clock output port
terminal.
(3) In the 16-bit mode, reading PTM(L) does not
latch the Timer(H) counter data in PTM(H). To
avoid generating a borrow from Timer(L) to
Timer(H), read the counter data after stopping
the timer by writing "0" to PTRUN(L).
S1C88655 TECHNICAL MANUAL
41H 40H 3FH 3EH 3DH
(4) For the reason below, pay attention to the
reload data write timing when changing the
interval of the programmable timer interrupts
while the programmable timer is running.
The programmable timer counts down at the
falling edge of the input clock and at the same
time it generates an interrupt if the counter
underflows. Then it starts loading the reload
data to the counter and the counter data is
determined at the next rising edge of the input
clock (period shown in as
(Reload data = 25H)
Input clock
Counter data
03H
(continuous mode)
Underflow (interrupt is generated)
Counter data is determined by reloading
Fig. 13.10.2 Reload timing for programmable timer
To avoid improper reloading, do not rewrite
the reload data after an interrupt occurs until
the counter data is determined including the
reloading period
using the OSC1 (low-speed clock) as the clock
source of the programmable timer and the CPU
is operating with the OSC3 (high-speed clock).
EPSON
13 PROGRAMMABLE TIMER
in the figure).
02H 01H 00H 25H
. Be especially careful when
24H
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