High-Frequency Warm-Up Counter Mode (Slow1 → Slow2 → Normal2 → Normal1) - Philips CEM2100/00 Service Manual

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10. 8-Bit TimerCounter (TC3, TC4)
10.1 Configuration
10.3.9.2 High-Frequency Warm-Up Counter Mode
bility is obtained. Before starting the timer, set SYSCR2<XEN> to 1 to oscillate the high-frequency clock.
When a match between the up-counter and the timer register (TTREG4, 3) value is detected after the timer
is started by setting TC4CR<TC4S> to 1, the counter is cleared by generating the INTTC4 interrupt
request. After stopping the timer in the INTTC4 interrupt service routine, clear SYSCR2<SYSCK> to 0 to
switch the system clock from the low-frequency to high-frequency, and then SYSCR2<XTEN> to 0 to
stop the low-frequency clock.
Table 10-9 Setting Time in High-Frequency Warm-Up Counter Mode
Example :After checking high-frequency clock oscillation stability with TC4 and 3, switching to the NORMAL1 mode
PINTTC4:
VINTTC4:
(SLOW1 → SLOW2 → NORMAL2 → NORMAL1)
In this mode, the warm-up period time from a stop of the high-frequency clock fc to the oscillation sta-
Minimum time Setting
(TTREG4, 3 = 0100H)
16 µs
SET
(SYSCR2).7
LD
(TC3CR), 63H
LD
(TC4CR), 05H
LD
(TTREG3), 0F800H
DI
SET
(EIRH). 1
EI
SET
(TC4CR).3
:
:
CLR
(TC4CR).3
CLR
(SYSCR2).5
CLR
(SYSCR2).6
RETI
:
:
DW
PINTTC4
Maximum time Setting
(TTREG4, 3 = FF00H)
4.08 ms
: SYSCR2<XEN>
1
: Sets TFF3=0, source clock fc, and 16-bit mode.
: Sets TFF4=0, and warm-up counter mode.
: Sets the warm-up time.
(The warm-up time depends on the oscillator characteristic.)
: IMF
0
: Enables the INTTC4.
: IMF
1
: Starts the TC4 and 3.
: Stops the TC4 and 3.
: SYSCR2<SYSCK>
(Switches the system clock to the high-frequency clock.)
: SYSCR2<XTEN>
0
(Stops the low-frequency clock.)
: INTTC4 vector table
Page 118
T5CL8
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