
2001 Microchip Technology Inc.
Advance Information
DS39541A-page 135
PIC18C601/801
12.0
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
Timer2 can be shut-off by clearing control bit TMR2ON
(T2CON register), to minimize power consumption.
Figure 12-1 is a simplified block diagram of the Timer2
module. The prescaler and postscaler selection of
Timer2 are controlled by this register.
12.1
Timer2 Operation
Timer2 can be used as the PWM time-base for the PWM
mode of the CCP module. The TMR2 register is read-
able 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 out-
put 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, or Watchdog Timer Reset)
TMR2 is not cleared when T2CON is written.
REGISTER 12-1:
T2CON REGISTER
Note:
Timer2 is disabled on POR.
U-0
R/W-0
—
TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0
bit 7
bit 0
bit 7
Unimplemented: Read as '0'
bit 6-3
TOUTPS3:TOUTPS0: Timer2 Output Postscale Select bits
0000
= 1:1 Postscale
0001
= 1:2 Postscale
1111
= 1:16 Postscale
bit 2
TMR2ON: Timer2 On bit
1
= Timer2 is on
0
= Timer2 is off
bit 1-0
T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits
00
= Prescaler is 1
01
= Prescaler is 4
1x
= Prescaler is 16
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
- n = Value at POR
’1’ = Bit is set
’0’ = Bit is cleared
x = Bit is unknown