PIC18F6410ESLASHPTSQTP datasheet(93/404 Pages) MICROCHIP

93 / 404 page

 2004 Microchip Technology Inc.

Preliminary

DS39635A-page 91

PIC18F6310/6410/8310/8410

7.2

16-Bit Mode

In 16-bit mode, the external memory interface can be

connected to external memories in three different

configurations:

• 16-bit Byte Write

• 16-bit Word Write

• 16-bit Byte Select

The configuration to be used is determined by the

WM1:WM0

bits

the

MEMCON

(MEMCON<1:0>). These three different configurations

allow the designer maximum flexibility in using both

8-bit and 16-bit devices with 16-bit data.

For all 16-bit modes, the Address Latch Enable (ALE)

pin indicates that the address bits, A<15:0>, are avail-

able on the external memory interface bus. Following the

address latch, the Output Enable signal (OE) will enable

both bytes of program memory at once to form a 16-bit

instruction word. The Chip Enable signal (CE) is active

at any time that the microcontroller accesses external

memory, whether reading or writing; it is inactive

(asserted high) whenever the device is in Sleep mode.

In Byte Select mode, JEDEC standard Flash memories

will require BA0 for the byte address line and one I/O line

to select between Byte and Word mode. The other 16-bit

modes do not need BA0. JEDEC standard static RAM

memories will use the UB or LB signals for byte selection.

7.2.1

16-BIT BYTE WRITE MODE

Figure 7-1 shows an example of 16-bit Byte Write

mode for PIC18F8310/8410 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>

ALE

D<15:8>

373

A<x:0>

D<7:0>

A<19:0>

A<x:0>

D<7:0>

373

WRH

WR(1)

Note 1: This signal only applies to table writes. See Section 6.1 “Table Reads and Table Writes”.

WRL

D<7:0>

(LSB)

(MSB)

PIC18F8410

D<7:0>

AD<15:8>

Address Bus

Data Bus

Control Lines

PIC18F6410E/PTSQTP Datasheet(PDF) 93 Page - Microchip Technology

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