PIC18F87J11_12 Datasheet, PDF (105/466 Pages) Microchip Technology – 64/80-Pin, High-Performance, 1-Mbit Flash Microcontrollers

PIC18F87J11 FAMILY
8.0 EXTERNAL MEMORY BUS
Note: The External Memory Bus (EMB) is not
implemented on 64-pin devices.
The External Memory Bus allows the device to access
external memory devices (such as Flash, EPROM,
SRAM, etc.) as program or data memory. It supports
both 8 and 16-Bit Data Width modes and three address
widths of up to 20 bits.
The bus is implemented with 28 pins, multiplexed
across four I/O ports. Three ports (PORTD, PORTE
and PORTH) are multiplexed with the address/data bus
for a total of 20 available lines, while PORTJ is
multiplexed with the bus control signals.
A list of the pins and their functions is provided in
Table 8-1.
TABLE 8-1: PIC18F87J11 FAMILY EXTERNAL BUS – I/O PORT FUNCTIONS
Name
Port
Bit
External Memory Bus Function
RD0/AD0
PORTD
0 Address Bit 0 or Data Bit 0
RD1/AD1
PORTD
1 Address Bit 1 or Data Bit 1
RD2/AD2
PORTD
2 Address Bit 2 or Data Bit 2
RD3/AD3
PORTD
3 Address Bit 3 or Data Bit 3
RD4/AD4
PORTD
4 Address Bit 4 or Data Bit 4
RD5/AD5
PORTD
5 Address Bit 5 or Data Bit 5
RD6/AD6
PORTD
6 Address Bit 6 or Data Bit 6
RD7/AD7
PORTD
7 Address Bit 7 or Data Bit 7
RE0/AD8
PORTE
0 Address Bit 8 or Data Bit 8
RE1/AD9
PORTE
1 Address Bit 9 or Data Bit 9
RE2/AD10
PORTE
2 Address Bit 10 or Data Bit 10
RE3/AD11
PORTE
3 Address Bit 11 or Data Bit 11
RE4/AD12
PORTE
4 Address Bit 12 or Data Bit 12
RE5/AD13
PORTE
5 Address Bit 13 or Data Bit 13
RE6/AD14
PORTE
6 Address Bit 14 or Data Bit 14
RE7/AD15
PORTE
7 Address Bit 15 or Data Bit 15
RH0/A16
PORTH
0 Address Bit 16
RH1/A17
PORTH
1 Address Bit 17
RH2/A18
PORTH
2 Address Bit 18
RH3/A19
PORTH
3 Address Bit 19
RJ0/ALE
PORTJ
0 Address Latch Enable (ALE) Control Pin
RJ1/OE
PORTJ
1 Output Enable (OE) Control Pin
RJ2/WRL
PORTJ
2 Write Low (WRL) Control Pin
RJ3/WRH
PORTJ
3 Write High (WRH) Control Pin
RJ4/BA0
PORTJ
4 Byte Address Bit 0 (BA0)
RJ5/CE
PORTJ
5 Chip Enable (CE) Control Pin
RJ6/LB
PORTJ
6 Lower Byte Enable (LB) Control Pin
RJ7/UB
PORTJ
7 Upper Byte Enable (UB) Control Pin
Note: For the sake of clarity, only I/O port and external bus assignments are shown here. One or more additional
multiplexed features may be available on some pins.
 2007-2012 Microchip Technology Inc.
DS39778E-page 105