PIC16F84A datasheet(58/337 Pages) MICROCHIP

58 / 337 page

PIC16C6X

DS30234D-page 58

5.5

PORTE and TRISE Register

PORTE has three pins, RE2/CS, RE1/WR, and

RE0/RD which are individually conﬁgurable as inputs

or outputs. These pins have Schmitt Trigger input buff-

ers.

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). In this mode the input buffers are TTL.

Figure 5-9 shows the TRISE register, which controls

the parallel slave port operation and also controls the

direction of the PORTE pins.

Applicable Devices

61 62 62A R62 63 R63 64 64A R64 65 65A R65 66 67

FIGURE 5-8:

PORTE BLOCK DIAGRAM

(IN I/O PORT MODE)

Data

bus

PORT

TRIS

RD PORT

Data Latch

TRIS Latch

RD TRIS

Schmitt

Trigger

input

buffer

I/O pin(1)

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

FIGURE 5-9:

TRISE REGISTER (ADDRESS 89h)

R-0

R/W-0

U-0

R/W-1

IBF

OBF

IBOV

PSPMODE

—

bit2

bit1

bit0

= Readable bit

W = Writable bit

= Unimplemented bit,

read as ‘0’

- n = Value at POR reset

bit7

bit0

bit 7 :

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

bit 6:

OBF: Output Buffer Full Status bit

1 = The output buffer still holds a previously written word

0 = The output buffer has been read

bit 5:

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

bit 4:

PSPMODE: Parallel Slave Port Mode Select bit

1 = Parallel slave port mode

0 = General purpose I/O mode

bit 3:

Unimplemented: Read as '0'

PORTE Data Direction Bits

bit 2:

Bit2: Direction Control bit for pin RE2/CS

1 = Input

0 = Output

bit 1:

Bit1: Direction Control bit for pin RE1/WR

1 = Input

0 = Output

bit 0:

Bit0: Direction Control bit for pin RE0/RD

1 = Input

0 = Output

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