P16F877 datasheet(38/218 Pages) MICROCHIP

38 / 218 page

PIC16F87X

DS30292C-page 36

 2001 Microchip Technology Inc.

3.5

PORTE and TRISE Register

PORTE and TRISE are not implemented on the

PIC16F873 or PIC16F876.

PORTE has three pins (RE0/RD/AN5, RE1/WR/AN6,

and RE2/CS/AN7) which are individually configureable

as inputs or outputs. These pins have Schmitt Trigger

input buffers.

The PORTE pins become the I/O control inputs for the

microprocessor port when bit PSPMODE (TRISE<4>) is

set. In this mode, the user must make certain that the

TRISE<2:0> bits are set, and that the pins are configured

as digital inputs. Also ensure that ADCON1 is configured

for digital I/O. In this mode, the input buffers are TTL.

trols the parallel slave port operation.

PORTE pins are multiplexed with analog inputs. When

selected for analog input, these pins will read as ’0’s.

TRISE controls the direction of the RE pins, even when

they are being used as analog inputs. The user must

make sure to keep the pins configured as inputs when

using them as analog inputs.

FIGURE 3-8:

PORTE BLOCK DIAGRAM

(IN I/O PORT MODE)

TABLE 3-9:

PORTE FUNCTIONS

TABLE 3-10:

SUMMARY OF REGISTERS ASSOCIATED WITH PORTE

Note:

On a Power-on Reset, these pins are con-

figured as analog inputs, and read as ‘0’.

Data

Bus

Port

TRIS

RD Port

Data Latch

TRIS Latch

Schmitt

Trigger

Input

Buffer

I/O pin(1)

Note 1: I/O pins have protection diodes to VDD and VSS.

TRIS

Name

Bit#

Buffer Type

Function

RE0/RD/AN5

bit0

ST/TTL(1)

I/O port pin or read control input in Parallel Slave Port mode or analog input:

=Idle

= Read operation. Contents of PORTD register are output to PORTD

I/O pins (if chip selected)

RE1/WR/AN6

bit1

ST/TTL(1)

I/O port pin or write control input in Parallel Slave Port mode or analog input:

=Idle

= Write operation. Value of PORTD I/O pins is latched into PORTD

RE2/CS/AN7

bit2

ST/TTL(1)

I/O port pin or chip select control input in Parallel Slave Port mode or analog input:

= Device is not selected

= Device is selected

Legend: ST = Schmitt Trigger input, TTL = TTL input

Note 1: Input buffers are Schmitt Triggers when in I/O mode and TTL buffers when in Parallel Slave Port mode.

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on:

POR, BOR

Value on

all other

RESETS

09h

PORTE

—

RE2

RE1

RE0

---- -xxx

---- -uuu

89h

TRISE

IBF

OBF

IBOV

PSPMODE

—

PORTE Data Direction Bits

0000 -111

9Fh

ADCON1

ADFM

—

PCFG3

PCFG2

PCFG1

PCFG0

--0- 0000

Legend: x = unknown, u = unchanged, - = unimplemented, read as ’0’. Shaded cells are not used by PORTE.

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