PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 90

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

FIGURE 8-11: PARALLEL SLAVE PORT WRITE WAVEFORMS
PIC18CXX2
8.6
The Parallel Slave Port is implemented on the 40-pin
devices only (PIC18C4X2).
PORTD operates as an 8-bit wide Parallel Slave Port,
or microprocessor port when control bit PSPMODE
(TRISE<4>) is set. In slave mode it is asynchronously
readable and writable by the external world through RD
control input pin RE0/RD and WR control input pin
RE1/WR.
It can directly interface to an 8-bit microprocessor data
bus. The external microprocessor can read or write the
PORTD latch as an 8-bit latch. Setting bit PSPMODE
enables port pin RE0/RD to be the RD input, RE1/WR
to be the WR input and RE2/CS to be the CS (chip
select) input. For this functionality, the corresponding
data direction bits of the TRISE register (TRISE<2:0>)
must be configured as inputs (set). The A/D port con-
figuration bits PCFG2:PCFG0 (ADCON1<2:0>) must
be set, which will configure pins RE2:RE0 as digital I/O.
A write to the PSP occurs when both the CS and WR
lines are first detected low. A read from the PSP occurs
when both the CS and RD lines are first detected low.
The PORTE I/O pins become control inputs for the
microprocessor 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 the ADCON1 is configured for digital I/O. In
this mode, the input buffers are TTL.
DS39026B-page 90
PORTD<7:0>
PSPIF
Parallel Slave Port
OBF
CS
WR
RD
IBF
Q1
Q2
Q3
Q4
Preliminary
Q1
Q2
FIGURE 8-10: PORTD AND PORTE BLOCK
One bit of PORTD
Q3
Data Bus
Set Interrupt Flag
PSPIF (PIR1<7>)
Note: I/O pin has protection diodes to V
WR LATD
or
PORTD
RD PORTD
RD LATD
Q4
Data Latch
Q
D
CK
DIAGRAM
(PARALLEL SLAVE PORT)
Q1
EN
EN
Q
D
7/99 Microchip Technology Inc.
Q2
Chip Select
Read
Write
Q3
TTL
TTL
TTL
TTL
DD
Q4
and V
SS
RDx
Pin
CS
WR
RD
.