Philips CEM2100/00 Service Manual page 150

2. Operational Description
2.2 System Clock Controller
2.2.4.4
Example 1 :Switching from NORMAL2 mode to SLOW1 mode.
Example 2 :Switching to the SLOW1 mode after low-frequency clock has stabilized.
PINTTC6:
VINTTC6:
SLOW mode
SLOW mode is controlled by the system control register 2 (SYSCR2).
The following is the methods to switch the mode with the warm-up counter.
(1) Switching from NORMAL2 mode to SLOW1 mode
First, set SYSCR2<SYSCK> to switch the main system clock to the low-frequency clock for
SLOW2 mode. Next, clear SYSCR2<XEN> to turn off high-frequency oscillation.
Note: The high-frequency clock can be continued oscillation in order to return to NORMAL2 mode from
SLOW mode quickly. Always turn off oscillation of high-frequency clock when switching from
SLOW mode to stop mode.
SET (SYSCR2). 5
CLR (SYSCR2). 7
SET (SYSCR2). 6
LD (TC5CR), 43H
LD (TC6CR), 05H
LDW (TTREG5), 8000H
DI
SET (EIRE). 2
EI
SET (TC6CR). 3
:
CLR (TC6CR). 3
SET (SYSCR2). 5
CLR (SYSCR2). 7
RETI
:
DW PINTTC6
←
; SYSCR2<SYSCK> 1
(Switches the main system clock to the low-frequency
clock for SLOW2)
←
; SYSCR2<XEN> 0
(Turns off high-frequency oscillation)
←
; SYSCR2<XTEN> 1
; Sets mode for TC6, 5 (16-bit mode, fs for source)
; Sets warming-up counter mode
; Sets warm-up time (Depend on oscillator accompanied)
←
; IMF 0
; Enables INTTC6
←
; IMF 1
; Starts TC6, 5
; Stops TC6, 5
←
; SYSCR2<SYSCK> 1
(Switches the main system clock to the low-frequency clock)
←
; SYSCR2<XEN> 0
(Turns off high-frequency oscillation)
; INTTC6 vector table
Page 28
T5CL8