PIC16C62B/72A
5.1
Timer1 Operation
5.0
TIMER1 MODULE
The Timer1 module timer/counter has the following fea-
tures:
Timer1 can operate in one of these modes:
• As a timer
• 16-bit timer/counter
• As a synchronous counter
• As an asynchronous counter
• Readable and writable
• Internal or external clock select
• Interrupt on overflow from FFFFh to 0000h
• Reset from CCP module trigger
The operating mode is determined by the clock select
bit, TMR1CS (T1CON<1>).
In timer mode, Timer1 increments every instruction
cycle. In counter mode, it increments on every rising
edge of the external clock input.
Timer1 has a control register, shown in Register 5-1.
Timer1 can be enabled/disabled by setting/clearing
control bit TMR1ON (T1CON<0>).
When the Timer1 oscillator is enabled (T1OSCEN is
set), the RC1/T1OSI and RC0/T1OSO/T1CKI pins
become inputs. That is, the TRISC<1:0> value is
ignored.
Figure 5-1 is a simplified block diagram of the Timer1
module.
Additional information on timer modules is available in
the PICmicro™ Mid-Range Reference Manual,
(DS33023).
Timer1 also has an internal “reset input”. This reset can
be generated by the CCP module as a special event
trigger (Section 7.0).
REGISTER 5-1:T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
U-0
U-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R
= Readable bit
—
—
T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON
bit0
W = Writable bit
U
bit7
= Unimplemented bit,
read as ‘0’
- n = Value at POR reset
bit 7-6: Unimplemented: Read as ’0’
bit 5-4: T1CKPS1:T1CKPS0: Timer1 Input Clock Prescale Select bits
11= 1:8 Prescale value
10= 1:4 Prescale value
01= 1:2 Prescale value
00= 1:1 Prescale value
bit 3:
bit 2:
T1OSCEN: Timer1 Oscillator Enable Control bit
1= Oscillator is enabled (TRISC<1:0> ignored)
0= Oscillator is shut off
(The oscillator is turned off to reduce power drain
T1SYNC: Timer1 External Clock Input Synchronization Control bit
TMR1CS = 1
1= Do not synchronize external clock input
0= Synchronize external clock input
TMR1CS = 0
This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.
bit 1:
bit 0:
TMR1CS: Timer1 Clock Source Select bit
1= External clock from pin RC0/T1OSO/T1CKI (on the rising edge)
0= Internal clock (FOSC/4)
TMR1ON: Timer1 On bit
1= Enables Timer1
0= Stops Timer1
1999 Microchip Technology Inc.
Preliminary
DS35008B-page 27
MICROCHIP [ MICROCHIP ]
