st2064b Sitronix Technology Corporation, st2064b Datasheet - Page 21

• Manufacturer Part Number: st2064b
• Description: 8 Bit Microcontroller With 64k Bytes Rom
• Manufacturer: Sitronix Technology Corporation

12.1.2 PRES
The prescaler PRES is an 16-bits counter as shown in FIGURE
12-1. Which provides four clock sources for base timer and
timer1, and it is controlled by register PRS. The instruction read
toward PRS will bring out the content of PRES and the
12.1.3 PREW
The prescaler PREW is an 8-bits counter as shown in FIGURE
12-1. PREW provides four clocks source for base timer and
Ver. 3.0
WRITE
Address Name
READ
$023
Bit 7:
Bit 6:
Bit 5:
Bit 7~0: PRS[7~0] : The low byte value of PRES counter
SRES : Prescaler Reset bit
SENA : Prescaler enable bit
SENT : Clock source(TCLK) selection for prescaller PRES
Write “ 1” to reset the prescaler (PRS[7~0])
0 = Disable prescaler counting
1 = Enable prescaler counting
0 = Clock source from system clock “ SYSCK”
1 = Clock source from external events “ INTX”
PRS
R/W
W
R
PRS[7]
SRES
Bit 7
TABLE 12-2 Prescaler Control Register (PRS)
PRS[6]
SENA
Bit 6
PRS[5]
SENT
Bit 5
PRS[4]
21/57
Bit 4
-
Instruction write toward PRS will reset, enable or select clock
sources for PRES.
When user set external interrupt as the input of PRES for event
counter, combining PRES and Timer1 will get a 16bit-event
counter.
timer1. It stops counting only if OSCX stops or hardware reset
occurs.
PRS[3]
Bit 3
-
PRS[2]
Bit 2
-
PRS[1]
Bit 1
-
PRS[0]
Bit 0
-
000 - - - - -
0000 0000
Default
ST2064B
5/8/09