
S1C88409 TECHNICAL MANUAL
EPSON
61
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Prescaler and Clock Control Circuit)
5.5.3 Prescaler division ratio selection
and output control
The prescaler has division ratio selection registers
and clock output control registers for the periph-
eral circuits, so the division ratio and the clock
output for each circuit can be controlled individu-
ally.
The prescaler division ratio is selected by the
division ratio selection register from 8 types set for
each peripheral circuit. The dividing clock is
output to the peripheral circuit by writing "1" to
the clock output control register.
The following shows the division ratio selection
register and the clock output control register for
each peripheral circuit.
16-bit programmable timer 0
Table 5.5.3.1 Division ratio and control registers
Division
ratio
fOSC3/4096
fOSC3/1024
fOSC3/256
fOSC3/128
fOSC3/64
fOSC3/32
fOSC3/8
fOSC3/2
Output
control
PRPRT0
register
"1": ON
"0": OFF
PST02
1
0
Selection register
PST01
1
0
1
0
PST00
1
0
1
0
1
0
1
0
16-bit programmable timer 0 (Clock source: OSC3)
Table 5.5.3.2 Division ratio and control registers
Division
ratio
fOSC1/128
fOSC1/64
fOSC1/32
fOSC1/16
fOSC1/8
fOSC1/4
fOSC1/2
fOSC1/1
Output
control
PRPRT0
register
"1": ON
"0": OFF
PST02
1
0
Selection register
PST01
1
0
1
0
PST00
1
0
1
0
1
0
1
0
16-bit programmable timer 0 (Clock source: OSC1)
The source clock (OSC1, OSC3) is selected by
the PRTF0 register.
16-bit programmable timer 1
Table 5.5.3.3 Division ratio and control registers
Division
ratio
fOSC3/4096
fOSC3/1024
fOSC3/256
fOSC3/128
fOSC3/64
fOSC3/32
fOSC3/8
fOSC3/2
Output
control
PRPRT1
register
"1": ON
"0": OFF
PST12
1
0
Selection register
PST11
1
0
1
0
PST10
1
0
1
0
1
0
1
0
16-bit programmable timer 1 (Clock source: OSC3)
Table 5.5.3.4 Division ratio and control registers
Division
ratio
fOSC1/128
fOSC1/64
fOSC1/32
fOSC1/16
fOSC1/8
fOSC1/4
fOSC1/2
fOSC1/1
Output
control
PRPRT1
register
"1": ON
"0": OFF
PST12
1
0
Selection register
PST11
1
0
1
0
PST10
1
0
1
0
1
0
1
0
16-bit programmable timer 1 (Clock source: OSC1)
The source clock (OSC1, OSC3) is selected by
the PRTF1 register.
8-bit programmable timer
Table 5.5.3.5 Division ratio and control registers
Division
ratio
fOSC3/256
fOSC3/128
fOSC3/64
fOSC3/32
fOSC3/16
fOSC3/8
fOSC3/4
fOSC3/2
Output
control
PRPRT2
register
"1": ON
"0": OFF
PST22
1
0
Selection register
PST21
1
0
1
0
PST20
1
0
1
0
1
0
1
0
8-bit programmable timer
FOUT1/FOUT3 clock output
Table 5.5.3.6 Division ratio and control registers
Division
ratio
fOSC1/128
fOSC1/64
fOSC1/32
fOSC1/16
fOSC1/8
fOSC1/4
fOSC1/2
fOSC1/1
Output
control
PRFO1
register
"1": ON
"0": OFF
PSF12
1
0
Selection register
PSF11
1
0
1
0
PSF10
1
0
1
0
1
0
1
0
FOUT1 clock
Table 5.5.3.7 Division ratio and control registers
Division
ratio
fOSC3/128
fOSC3/64
fOSC3/32
fOSC3/16
fOSC3/8
fOSC3/4
fOSC3/2
fOSC3/1
Output
control
PRFO3
register
"1": ON
"0": OFF
PSF32
1
0
Selection register
PSF31
1
0
1
0
PSF30
1
0
1
0
1
0
1
0
FOUT3 clock