Datasheet

© 2009 Microchip Technology Inc. DS39775C-page 111
PIC18F87J50 FAMILY
7.6.1 16-BIT BYTE WRITE MODE
Figure 7-1 shows an example of 16-Bit Byte Write
mode for PIC18F87J10 family devices. This mode is
used for two separate 8-bit memories connected for
16-bit operation. This generally includes basic EPROM
and Flash devices. It allows table writes to byte-wide
external memories.
During a TBLWT instruction cycle, the TABLAT data is
presented on the upper and lower bytes of the
AD15:AD0 bus. The appropriate WRH
or WRL control
line is strobed on the LSb of the TBLPTR.
FIGURE 7-1: 16-BIT BYTE WRITE MODE EXAMPLE
AD<7:0>
A<19:16>
(1)
ALE
D<15:8>
373
A<x:0>
D<7:0>
A<19:0>
A<x:0>
D<7:0>
373
OE
WRH
OE OE
WR
(2)
WR
(2)
CE
CE
Note 1: Upper order address lines are used only for 20-bit address widths.
2: This signal only applies to table writes. See Section 6.1 “Table Reads and Table Writes”.
WRL
D<7:0>
(LSB)
(MSB)
PIC18F87J50
D<7:0>
AD<15:8>
Address Bus
Data Bus
Control Lines
CE