PIC17C7XX Datasheet, PDF (95/328 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers with 10-bit A/D

12.0 TIMER0
The Timer0 module consists of a 16-bit timer/counter,
TMR0. The high byte is register TMR0H and the low
byte is register TMR0L. A software programmable 8-bit
prescaler makes Timer0 an effective 24-bit overflow
timer. The clock source is software programmable as
either the internal instruction clock or an external clock
on the RA1/T0CKI pin. The control bits for this module
are in register T0STA (Figure 12-1).
PIC17C7XX
FIGURE 12-1: T0STA REGISTER (ADDRESS: 05h, UNBANKED)
R/W - 0 R/W - 0
INTEDG T0SE
bit7
R/W - 0
T0CS
R/W - 0
T0PS3
R/W - 0
T0PS2
R/W - 0
T0PS1
R/W - 0
T0PS0
bit 7:
INTEDG: RA0/INT Pin Interrupt Edge Select bit
This bit selects the edge upon which the interrupt is detected
1 = Rising edge of RA0/INT pin generates interrupt
0 = Falling edge of RA0/INT pin generates interrupt
U-0
—
bit0
R = Readable bit
W = Writable bit
U = Unimplemented,
Read as '0'
-n = Value at POR reset
bit 6:
T0SE: Timer0 Clock Input Edge Select bit
This bit selects the edge upon which TMR0 will increment
When T0CS = 0 (External Clock)
1 = Rising edge of RA1/T0CKI pin increments TMR0 and/or sets the T0CKIF bit
0 = Falling edge of RA1/T0CKI pin increments TMR0 and/or sets the T0CKIF bit
When T0CS = 1 (Internal Clock)
Don’t care
bit 5:
T0CS: Timer0 Clock Source Select bit
This bit selects the clock source for TMR0.
1 = Internal instruction clock cycle (TCY)
0 = External Clock input on the T0CKI pin
bit 4-1: T0PS3:T0PS0: Timer0 Prescale Selection bits
These bits select the prescale value for TMR0.
T0PS3:T0PS0 Prescale Value
0000
0001
0010
0011
0100
0101
0110
0111
1xxx
1:1
1:2
1:4
1:8
1:16
1:32
1:64
1:128
1:256
bit 0: Unimplemented: Read as '0'
© 1998 Microchip Technology Inc.
DS30289A-page 95