Datasheet

 2010 Microchip Technology Inc. DS41326E-page 27
PIC16F526
6.0 I/O PORT
As with any other register, the I/O register(s) can be
written and read under program control. However, read
instructions (e.g., MOVF PORTB,W) always read the I/O
pins independent of the pin’s Input/Output modes. On
Reset, all I/O ports are defined as input (inputs are at high-
impedance) since the I/O control registers are all set.
6.1 PORTB
PORTB is a 6-bit I/O register. Only the low-order 6 bits
are used (RB<5:0>). Bits 7 and 6 are unimplemented
and read as ‘0’s. Please note that RB3 is an input-only
pin. The Configuration Word can set several I/O’s to
alternate functions. When acting as alternate functions,
the pins will read as ‘0’ during a port read. Pins RB0,
RB1, RB3 and RB4 can be configured with weak pull-
ups and also for wake-up on change. The wake-up on
change and weak pull-up functions are not pin
selectable. If RB3/MCLR
is configured as MCLR, weak
pull-up is always on and wake-up on change for this pin
is not enabled.
6.2 PORTC
PORTC is a 6-bit I/O register. Only the low-order 6 bits
are used (RC<5:0>). Bits 7 and 6 are unimplemented
and read as ‘0’s.
6.3 TRIS Register
The Output Driver Control register is loaded with the
contents of the W register by executing the TRIS f
instruction. A ‘1’ from a TRIS register bit puts the
corresponding output driver in a High-Impedance
mode. A ‘0’ puts the contents of the output data latch
on the selected pins, enabling the output buffer. The
exceptions are RB3, which is input-only and the T0CKI
pin, which may be controlled by the OPTION register.
See Register 4-2.
TRIS registers are “write-only”. Active bits in these
registers are set (output drivers disabled) upon Reset.
TABLE 6-1: WEAK PULL-UP ENABLED PINS
Device RB0 Weak Pull-up RB1 Weak Pull-up RB3 Weak Pull-up
(1)
RB4 Weak Pull-up
PIC16F526 Yes Yes Yes Yes
Note 1: When MCLREN = 1, the weak pull-up on RB3/MCLR
is always enabled.
REGISTER 6-1: PORTB: PORTB REGISTER
U-0 U-0 R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x
— — RB5 RB4 RB3 RB2 RB1 RB0
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 Unimplemented: Read as ‘0’
bit 5-0 RB<5:0>: PORTB I/O Pin bits
1 = Port pin is >V
IH min.
0 = Port pin is <V
IL max.