Datasheet

© 2009 Microchip Technology Inc. DS40044G-page 37
PIC16F627A/628A/648A
TABLE 5-1: PORTA FUNCTIONS
TABLE 5-2: SUMMARY OF REGISTERS ASSOCIATED WITH PORTA
Name Function
Input
Type
Output
Type
Description
RA0/AN0 RA0 ST CMOS Bidirectional I/O port
AN0 AN — Analog comparator input
RA1/AN1 RA1 ST CMOS Bidirectional I/O port
AN1 AN — Analog comparator input
RA2/AN2/V
REF RA2 ST CMOS Bidirectional I/O port
AN2 AN — Analog comparator input
VREF —ANVREF output
RA3/AN3/CMP1 RA3 ST CMOS Bidirectional I/O port
AN3 AN — Analog comparator input
CMP1 — CMOS Comparator 1 output
RA4/T0CKI/CMP2 RA4 ST OD Bidirectional I/O port. Output is open drain type.
T0CKI ST — External clock input for TMR0 or comparator output
CMP2 — OD Comparator 2 output
RA5/MCLR
/VPP RA5 ST — Input port
MCLR
ST — Master clear. When configured as MCLR, this pin is an
active low Reset to the device. Voltage on MCLR
/VPP must
not exceed V
DD during normal device operation.
V
PP HV —
Programming voltage input
RA6/OSC2/CLKOUT RA6 ST CMOS Bidirectional I/O port
OSC2 — XTAL Oscillator crystal output. Connects to crystal resonator in
Crystal Oscillator mode.
CLKOUT — CMOS In RC or INTOSC mode. OSC2 pin can output CLKOUT,
which has 1/4 the frequency of OSC1.
RA7/OSC1/CLKIN RA7 ST CMOS Bidirectional I/O port
OSC1 XTAL — Oscillator crystal input. Connects to crystal resonator in
Crystal Oscillator mode.
CLKIN ST — External clock source input. RC biasing pin.
Legend: O = Output CMOS = CMOS Output P = Power
— = Not used I = Input ST = Schmitt Trigger Input
TTL = TTL Input OD = Open Drain Output AN = Analog
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on
POR
Value on
All Other
Resets
05h PORTA RA7 RA6
RA5
(1)
RA4 RA3 RA2 RA1 RA0 xxxx 0000 qqqu 0000
85h TRISA TRISA7 TRISA6 TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 1111 1111 1111 1111
1Fh CMCON
C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 0000 0000 0000 0000
9Fh VRCON VREN VROE
VRR — VR3 VR2 VR1 VR0 000- 0000 000- 0000
Legend: - = Unimplemented locations read as ‘0’, u = unchanged, x = unknown, q = value depends on condition. Shaded cells
are not used for PORTA.
Note 1: MCLRE configuration bit sets RA5 functionality.