PIC18FXX20
11.0
TIMER0 MODULE
The Timer0 module has the following features:
• Software selectable as an 8-bit or 16-bit
timer/counter
• Readable and writable
• Dedicated 8-bit software programmable prescaler
• Clock source selectable to be external or internal
• Interrupt-on-overflow from FFh to 00h in 8-bit
mode and FFFFh to 0000h in 16-bit mode
• Edge select for external clock
Timer0 module in 8-bit mode and Figure 11-2 shows a
simplified block diagram of the Timer0 module in 16-bit
mode.
The T0CON register (Register 11-1) is a readable and
writable register that controls all the aspects of Timer0,
including the prescale selection.
REGISTER 11-1:
T0CON: TIMER0 CONTROL REGISTER
R/W-1
TMR0ON
bit 7
R/W-1
T08BIT
R/W-1
T0CS
R/W-1
T0SE
R/W-1
PSA
R/W-1
T0PS2
R/W-1
T0PS1
R/W-1
T0PS0
bit 0
bit 7
TMR0ON:
Timer0 On/Off Control bit
1
= Enables Timer0
0
= Stops Timer0
T08BIT:
Timer0 8-bit/16-bit Control bit
1
= Timer0 is configured as an 8-bit timer/counter
0
= Timer0 is configured as a 16-bit timer/counter
T0CS:
Timer0 Clock Source Select bit
1
= Transition on T0CKI pin
0
= Internal instruction cycle clock (CLKO)
T0SE:
Timer0 Source Edge Select bit
1
= Increment on high-to-low transition on T0CKI pin
0
= Increment on low-to-high transition on T0CKI pin
PSA:
Timer0 Prescaler Assignment bit
1
= TImer0 prescaler is NOT assigned. Timer0 clock input bypasses prescaler.
0
= Timer0 prescaler is assigned. Timer0 clock input comes from prescaler output.
T0PS2:T0PS0:
Timer0 Prescaler Select bits
111
= 1:256 prescale value
110
= 1:128 prescale value
101
= 1:64 prescale value
100
= 1:32 prescale value
011
= 1:16 prescale value
010
= 1:8 prescale value
001
= 1:4 prescale value
000
= 1:2 prescale value
Legend:
R = Readable bit
- n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 6
bit 5
bit 4
bit 3
bit 2-0
2003 Microchip Technology Inc.
Advance Information
DS39609A-page 131
MICROCHIP [ MICROCHIP TECHNOLOGY ]
