PIC12F635/PIC16F636/639
4.2.4.5
RA4/T1G/OSC2/CLKOUT
4.2.4.6
RA5/T1CKI/OSC1/CLKIN
Figure 4-5 shows the diagram for this pin. The RA4 pin
is configurable to function as one of the following:
Figure 4-6 shows the diagram for this pin. The RA5 pin
is configurable to function as one of the following:
• a general purpose I/O
• a Timer1 gate input
• a crystal/resonator connection
• a clock output
• a general purpose I/O
• a Timer1 clock input
• a crystal/resonator connection
• a clock input
FIGURE 4-5:
BLOCK DIAGRAM OF RA4
FIGURE 4-6:
BLOCK DIAGRAM OF RA5
Data Bus
D
Data Bus
D
CLK(1) Modes
VDD
CLK(1) Modes
VDD
Q
Q
Q
Q
WR
WR
CK
CK
WPUDA
WPUDA
Weak
Weak
RAPU
RAPU
RD
RD
WPUDA
WPUDA
Weak
Weak
D
Q
Q
D
Q
Q
VSS
VSS
WR
WR
WDA
CK
CK
WDA
Oscillator
Circuit
RD
WDA
RD
WDA
Oscillator
Circuit
OSC1
VDD
CLKOUT
Enable
OSC2
VDD
D
Q
Q
FOSC/4
1
0
WR
PORTA
CK
D
Q
Q
WR
PORTA
CK
I/O pin
I/O pin
CLKOUT
Enable
D
Q
Q
VSS
WR
TRISA
CK
D
Q
Q
VSS
INTOSC/
RC/EC(2)
WR
TRISA
INTOSC
Mode
CK
RD
TRISA
CLKOUT
Enable
(2)
RD
TRISA
RD
PORTA
XTAL
D
Q
Q
RD
PORTA
Q
Q
D
CK
WR
IOCA
D
Q
Q
Q1
EN
Q
Q
D
CK
WR
IOCA
RD
IOCA
EN
Q1
D
RD
IOCA
D
EN
Interrupt-on-
change
EN
Interrupt-on-
change
RD PORTA
RD PORTA
T1G To Timer1
T1G To Timer1
Note 1: Oscillator modes are XT, HS, LP and LPTMR1.
Note 1: Oscillator modes are XT, HS, LP, LPTMR1 and
CLKOUT Enable.
2: When using Timer1 with LP oscillator, the
Schmitt Trigger is bypassed.
2: With CLKOUT option.
© 2007 Microchip Technology Inc.
DS41232D-page 55
MICROCHIP [ MICROCHIP ]
