PIC16LF877A-I Datasheet, PDF (51/234 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers

4.5 PORTE and TRISE Register
Note: PORTE and TRISE are not implemented
on the 28-pin devices.
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.
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 config-
ured for digital I/O. In this mode, the input buffers are
TTL.
Register 4-1 shows the TRISE register which also
controls 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.
Note: On a Power-on Reset, these pins are
configured as analog inputs and read as ‘0’.
PIC16F87XA
FIGURE 4-9:
PORTE BLOCK DIAGRAM
(IN I/O PORT MODE)
Data
Bus
WR
Port
WR
TRIS
Data Latch
DQ
CK
TRIS Latch
DQ
CK
RD
TRIS
I/O pin⁽¹⁾
Schmitt
Trigger
Input
Buffer
RD Port
Q
D
ENEN
Note 1: I/O pins have protection diodes to VDD and VSS.
TABLE 4-9: PORTE FUNCTIONS
Name
Bit# Buffer Type
Function
I/O port pin or read control input in Parallel Slave Port mode or analog input:
RE0/RD/AN5 bit 0
ST/TTL⁽¹⁾
RD
1 = Idle
0 = Read operation. Contents of PORTD register are output to PORTD
I/O pins (if chip selected).
I/O port pin or write control input in Parallel Slave Port mode or analog input:
RE1/WR/AN6 bit 1
ST/TTL⁽¹⁾
WR
1 = Idle
0 = Write operation. Value of PORTD I/O pins is latched into PORTD
register (if chip selected).
I/O port pin or chip select control input in Parallel Slave Port mode or analog input:
RE2/CS/AN7 bit 2
ST/TTL⁽¹⁾
CS
1 = Device is not selected
0 = 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.
 2003 Microchip Technology Inc.
DS39582B-page 49