Datasheet

 2011 Microchip Technology Inc. DS39932D-page 215
PIC18F46J11 FAMILY
15.0 TIMER3 MODULE
The Timer3 timer/counter module incorporates these
features:
• Software selectable operation as a 16-bit timer or
counter
• Readable and writable 8-bit registers (TMR3H
and TMR3L)
• Selectable clock source (internal or external) with
device clock or Timer1 oscillator internal options
• Interrupt-on-overflow
• Module Reset on ECCP Special Event Trigger
A simplified block diagram of the Timer3 module is
shown in Figure 15-1.
The Timer3 module is controlled through the T3CON
register (Register 15-1). It also selects the clock source
options for the ECCP modules; see Section 18.1.1
“ECCP Module and Timer Resources” for more
information.
The F
OSC clock source (TMR3CS<1:0> = 01) should
not be used with the ECCP capture/compare features.
If the timer will be used with the capture or compare
features, always select one of the other timer clocking
options.
REGISTER 15-1: T3CON: TIMER3 CONTROL REGISTER (ACCESS F79h)
R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0
TMR3CS1 TMR3CS0 T3CKPS1 T3CKPS0
— T3SYNC RD16 TMR3ON
bit 7 bit 0
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
bit 7-6 TMR3CS<1:0>: Timer3 Clock Source Select bits
(2)
10 = Timer3 clock source is the T3CKI input pin (assigned in the PPS module)
01 = Timer3 clock source is the system clock (F
OSC)
(1)
00 = Timer3 clock source is the instruction clock (FOSC/4)
bit 5-4 T3CKPS<1:0>: Timer3 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 Reserved: Program as ‘0’
bit 2 T3SYNC
: Timer3 External Clock Input Synchronization Control bit
When TMR3CS
<1:0> = 10:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR3CS
<1:0> = 0x:
This bit is ignored; Timer3 uses the internal clock.
bit 1 RD16: 16-Bit Read/Write Mode Enable bit
1 = Enables register read/write of Timer3 in one 16-bit operation
0 = Enables register read/write of Timer3 in two 8-bit operations
bit 0 TMR3ON: Timer3 On bit
1 = Enables Timer3
0 = Stops Timer3
Note 1: The F
OSC clock source should not be selected if the timer will be used with the ECCP capture/compare
features.
2: When switching clock sources and using the clock prescaler, write to TMR3L afterwards to reset the inter-
nal prescaler count to 0.