PIC16F87XA
7.0
TIMER2 MODULE
Additional information on timer modules is available in
the PICmicro™ Mid-Range MCU Family Reference
Manual (DS33023).
Timer2 is an 8-bit timer with a prescaler and a
postscaler. It can be used as the PWM time-base for
the PWM mode of the CCP module(s). The TMR2 reg-
ister is readable and writable, and is cleared on any
device RESET.
The input clock (F
OSC
/4) has a prescale option of
1:1, 1:4, or 1:16, selected by control bits
T2CKPS1:T2CKPS0 (T2CON<1:0>).
The Timer2 module has an 8-bit period register, PR2.
Timer2 increments from 00h until it matches PR2 and
then resets to 00h on the next increment cycle. PR2 is
a readable and writable register. The PR2 register is
initialized to FFh upon RESET.
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, (PIR1<1>)).
Timer2 can be shut-off by clearing control bit, TMR2ON
(T2CON<2>), to minimize power consumption.
FIGURE 7-1:
Sets Flag
bit TMR2IF
TMR2
Output
(1)
RESET
Postscaler
1:1 to 1:16
4
T2OUTPS3:
T2OUTPS0
TIMER2 BLOCK DIAGRAM
TMR2 Reg
Comparator
Prescaler
1:1, 1:4, 1:16
2
T2CKPS1:
T2CKPS0
F
OSC
/4
EQ
PR2 Reg
Note 1:
TMR2 register output can be software selected by the
SSP module as a baud clock.
REGISTER 7-1:
T2CON: TIMER2 CONTROL REGISTER (ADDRESS 12h)
U-0
—
bit 7
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
bit 0
TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0
bit 7
bit 6-3
Unimplemented:
Read as '0'
TOUTPS3:TOUTPS0:
Timer2 Output Postscale Select bits
0000
= 1:1 Postscale
0001
= 1:2 Postscale
0010
= 1:3 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
bit 2
bit 1-0
2001 Microchip Technology Inc.
Advance Information
DS39582A-page 59
MICROCHIP [ MICROCHIP TECHNOLOGY ]
