INTERFACING WITH EXTERNAL MEMORY

Figure 15-12 shows an 8-bit system with both flash and RAM. The flash is the lower half of mem- ory, and the RAM is the upper half. This system configuration uses the most-significant address bit (AD15) as the chip-select signal and ALE as the address-latch signal.

 

 

CS#

CS#

 

AD15

 

 

 

 

AD14:8

 

A14:8

A12:8

 

 

 

D7:0

D7:0

 

8XC196

 

32K×8

 

8K×8

 

Flash

 

RAM

 

 

 

 

 

(28F256)

 

 

AD7:0

74AC

A7:0

A7:0

 

373

A7:0

 

 

 

 

 

 

LE

 

 

 

ALE

 

 

 

 

 

 

OE#

OE#

WE#

RD#

 

 

 

 

WR#

 

 

 

 

 

 

 

 

A3140-01

Figure 15-12. 8-bit System with Flash and RAM

15-23

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Intel 8XC196MC, 8XC196MD, 8XC196MH manual Cs#, Ale Oe# We# Rd# Wr#