PIC18F258 Datasheet, PDF (117/384 Pages) Microchip Technology – High Performance, 28/40-Pin Enhanced FLASH Microcontrollers with CAN

PIC18FXX8
13.0 TIMER2 MODULE
The Timer2 module timer has the following features:
• 8-bit timer (TMR2 register)
• 8-bit period register (PR2)
• Readable and writable (both registers)
• Software programmable prescaler (1:1, 1:4, 1:16)
• Software programmable postscaler (1:1 to 1:16)
• Interrupt on TMR2 match of PR2
• SSP module optional use of TMR2 output to
generate clock shift
Register 13-1 shows the Timer2 Control register.
Timer2 can be shut-off by clearing control bit TMR2ON
(T2CON register) to minimize power consumption.
Figure 13-1 is a simplified block diagram of the Timer2
module. The prescaler and postscaler selection of
Timer2 are controlled by this register.
13.1 Timer2 Operation
Timer2 can be used as the PWM time-base for the
PWM mode of the CCP module. The TMR2 register is
readable and writable, and is cleared on any device
RESET. The input clock (FOSC/4) has a prescale option
of 1:1, 1:4, or 1:16, selected by control bits
T2CKPS1:T2CKPS0 (T2CON Register). The match
output of TMR2 goes through a 4-bit postscaler (which
gives a 1:1 to 1:16 scaling inclusive) to generate a
TMR2 interrupt (latched in flag bit TMR2IF, PIR
registers).
The prescaler and postscaler counters are cleared
when any of the following occurs:
• A write to the TMR2 register
• A write to the T2CON register
• Any device RESET (Power-on Reset, MCLR
Reset, Watchdog Timer Reset, or Brown-out
Reset)
TMR2 is not cleared when T2CON is written.
Note: Timer2 is disabled on POR.
REGISTER 13-1: T2CON REGISTER
U-0
—
bit 7
R/W-0 R/W-0 R/W-0 R/W-0
TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0
R/W-0
TMR2ON
R/W-0
T2CKPS1
R/W-0
T2CKPS0
bit 0
bit 7
bit 6-3
bit 2
bit 1-0
Unimplemented: Read as '0'
TOUTPS3:TOUTPS0: Timer2 Output Postscale Select bits
0000 = 1:1 Postscale
0001 = 1:2 Postscale
•
•
•
1111 = 1:16 Postscale
TMR2ON: Timer2 On bit
1 = Timer2 is on
0 = Timer2 is off
T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits
00 = Prescaler is 1
01 = Prescaler is 4
1x = Prescaler is 16
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
 2002 Microchip Technology Inc.
Preliminary
DS41159B-page 115