PIC16C74AT-20I View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16C74AT-20I

8-Bit CMOS Microcontrollers with A/D Converter

Microchip Technology 

PIC16C7X

5.5 PORTE and TRISE Register

Applicable Devices

72 73 73A 74 74A 76 77

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

and RE2/CS/AN7, which are individually configurable

as inputs or outputs. These pins have Schmitt Trigger

input buffers.

I/O PORTE becomes control inputs for the micropro-

cessor port when bit PSPMODE (TRISE<4>) is set. In

this mode, the user must make sure that the

TRISE<2:0> bits are set (pins are configured as digital

inputs) and that register ADCON1 is configured for dig-

ital I/O. In this mode the input buffers are TTL.

Figure 5-9 shows the TRISE register, which also con-

trols the parallel slave port operation.

PORTE pins are multiplexed with analog inputs. The

operation of these pins is selected by control bits in the

ADCON1 register. When selected as an 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 5-9: TRISE REGISTER (ADDRESS 89h)

Note: On a Power-on Reset these pins are con-

figured as analog inputs.

FIGURE 5-8: PORTE BLOCK DIAGRAM (IN

I/O PORT MODE)

Data

bus

WR

PORT

DQ

CK

I/O pin(1)

WR

TRIS

Data Latch

DQ

CK

TRIS Latch

Schmitt

Trigger

input

buffer

RD TRIS

Q

D

RD PORT

ENEN

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

R-0

IBF

bit7

bit 7 :

bit 6:

bit 5:

bit 4:

bit 3:

bit 2:

bit 1:

bit 0:

R-0

OBF

R/W-0 R/W-0

U-0

IBOV PSPMODE —

R/W-1

bit2

R/W-1

bit1

IBF: Input Buffer Full Status bit

1 = A word has been received and is waiting to be read by the CPU

0 = No word has been received

R/W-1

bit0

bit0

R = Readable bit

W = Writable bit

U = Unimplemented bit,

read as ‘0’

- n = Value at POR reset

OBF: Output Buffer Full Status bit

1 = The output buffer still holds a previously written word

0 = The output buffer has been read

IBOV: Input Buffer Overflow Detect bit (in microprocessor mode)

1 = A write occurred when a previously input word has not been read (must be cleared in software)

0 = No overflow occurred

PSPMODE: Parallel Slave Port Mode Select bit

1 = Parallel slave port mode

0 = General purpose I/O mode

Unimplemented: Read as '0'

PORTE Data Direction Bits

Bit2: Direction Control bit for pin RE2/CS/AN7

1 = Input

0 = Output

Bit1: Direction Control bit for pin RE1/WR/AN6

1 = Input

0 = Output

Bit0: Direction Control bit for pin RE0/RD/AN5

1 = Input

0 = Output

© 1997 Microchip Technology Inc.

DS30390E-page 51

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