PIC16F870-I/SO View Datasheet(PDF) - Microchip Technology
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Description
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PIC16F870-I/SO Datasheet PDF : 156 Pages
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PIC16F870/871
3.5 PORTE and TRISE Register
This section is not applicable to the PIC16F870.
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). Ensure ADCON1 is configured for digital I/O. In
this mode, the input buffers are TTL.
Register 3-1 shows the TRISE Register, which also
controls the parallel slave port operation.
PORTE pins are multiplexed with analog inputs. 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.
Note: On a Power-on Reset, these pins are con-
figured as analog inputs.
FIGURE 3-7: PORTE BLOCK DIAGRAM (IN
I/O PORT MODE)
Data
Bus
DQ
WR
PORT
CK
I/O pin(1)
WR
TRIS
Data Latch
DQ
CK
TRIS Latch
Schmitt
Trigger
input
buffer
RD TRIS
Q
D
EN
RD PORT
Note 1: I/O pins have protection diodes to VDD and VSS.
REGISTER 3-1: TRISE REGISTER (ADDRESS 89h)
R-0
IBF
bit7
bit 7 :
bit 6:
bit 5:
bit 4:
bit 3:
bit 2:
bit 1:
bit 0:
R-0 R/W-0
R/W-0
U-0
R/W-1 R/W-1 R/W-1
OBF IBOV PSPMODE —
bit2
bit1
bit0
R = Readable bit
bit0
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n= Value at POR reset
Parallel Slave Port Status/Control Bits
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
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
DS30569A-page 34
Preliminary
© 1999 Microchip Technology Inc.
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