PIC16C620 Microchip Technology, PIC16C620 Datasheet - Page 34

• Manufacturer Part Number: PIC16C620
• Description: EPROM-Based 8-Bit CMOS Microcontroller
• Manufacturer: Microchip Technology

PIC16C62X
6.3
An 8-bit counter is available as a prescaler for the
Timer0 module, or as a postscaler for the Watchdog
Timer, respectively (Figure 6-6). For simplicity, this
counter is being referred to as “prescaler” throughout
this data sheet. Note that there is only one prescaler
available which is mutually exclusive between the
Timer0 module and the Watchdog Timer. Thus, a
prescaler assignment for the Timer0 module means
that there is no prescaler for the Watchdog Timer, and
vice-versa.
FIGURE 6-6:
DS30235G-page 34
CLKOUT (=Fosc/4)
WDT Enable bit
Note: T0SE, T0CS, PSA, PS0-PS2 are bits in the OPTION register.
T0CKI
Watchdog
pin
Timer
Prescaler
BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
T0SE
0
1
PSA
M
U
X
0
1
T0CS
M
U
X
0
8-bit Prescaler
8-to-1MUX
Time-out
8
M U X
WDT
Preliminary
1
0
1
PSA
M
U
X
The PSA and PS2:PS0 bits (OPTION<3:0>) determine
the prescaler assignment and prescale ratio.
When assigned to the Timer0 module, all instructions
writing to the TMR0 register (e.g., CLRF 1, MOVWF 1,
BSF 1,x....etc.)
assigned to WDT, a CLRWDT instruction will clear the
prescaler along with the Watchdog Timer. The
prescaler is not readable or writable.
PSA
PS0 - PS2
Cycles
SYNC
2
will
clear
1998 Microchip Technology Inc.
TMR0 reg
Data Bus
the
8
prescaler. When
Set flag bit T0IF
on Overflow