PIC18F87J11_12 Datasheet, PDF (209/466 Pages) Microchip Technology – 64/80-Pin, High-Performance, 1-Mbit Flash Microcontrollers

PIC18F87J11 FAMILY
17.0 TIMER4 MODULE
The Timer4 timer module has the following features:
• 8-bit timer register (TMR4)
• 8-bit period register (PR4)
• Readable and writable (both registers)
• Software programmable prescaler (1:1, 1:4, 1:16)
• Software programmable postscaler (1:1 to 1:16)
• Interrupt on TMR4 match of PR4
Timer4 has a control register shown in Register 17-1.
Timer4 can be shut off by clearing control bit, TMR4ON
(T4CON<2>), to minimize power consumption. The
prescaler and postscaler selection of Timer4 are also
controlled by this register. Figure 17-1 is a simplified
block diagram of the Timer4 module.
17.1 Timer4 Operation
Timer4 can be used as the PWM time base for the
PWM mode of the ECCPx/CCPx modules. The TMR4
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
T4CKPS<1:0> (T4CON<1:0>). The match output of
TMR4 goes through a 4-bit postscaler (which gives a
1:1 to 1:16 scaling inclusive) to generate a TMR4
interrupt, latched in flag bit, TMR4IF (PIR3<3>).
The prescaler and postscaler counters are cleared
when any of the following occurs:
• a write to the TMR4 register
• a write to the T4CON register
• any device Reset (Power-on Reset, MCLR Reset,
Watchdog Timer Reset or Brown-out Reset)
TMR4 is not cleared when T4CON is written.
REGISTER 17-1: T4CON: TIMER4 CONTROL REGISTER
U-0
—
bit 7
R/W-0
R/W-0
R/W-0
R/W-0
T4OUTPS3 T4OUTPS2 T4OUTPS1 T4OUTPS0
R/W-0
TMR4ON
R/W-0
T4CKPS1
R/W-0
T4CKPS0
bit 0
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 7
bit 6-3
bit 2
bit 1-0
Unimplemented: Read as ‘0’
T4OUTPS<3:0>: Timer4 Output Postscale Select bits
0000 = 1:1 Postscale
0001 = 1:2 Postscale
•
•
•
1111 = 1:16 Postscale
TMR4ON: Timer4 On bit
1 = Timer4 is on
0 = Timer4 is off
T4CKPS<1:0>: Timer4 Clock Prescale Select bits
00 = Prescaler is 1
01 = Prescaler is 4
1x = Prescaler is 16
 2007-2012 Microchip Technology Inc.
DS39778E-page 209