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8XC196Kx,8XC196Jx,87C196CA microcontroller family user's manual.1995.pdf
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8XC196Kx, Jx, CA USER’S MANUAL

15.7.5 Design Considerations

In all bus timing modes, for 16-bit bus-width operation, latch the upper and lower address/data lines. In modes 1 and 2, for 8-bit bus-width operation, also latch the upper and lower address/data lines; the upper address lines are not driven throughout the entire bus cycle (see Figures 15-22 and 15-23). In modes 0 and 3, for 8-bit bus-width operation, latch only the lower address/data lines. In these modes, it is not necessary to latch the upper address lines because these lines are driven throughout the entire bus cycle.

15-34

INTERFACING WITH EXTERNAL MEMORY

 

TOSC

 

 

XTAL 1

 

 

 

 

TCHCL

TCLCL

TXHCH

 

 

CLKOUT

 

 

 

 

TCHLH

TCLLL

 

 

 

TLHLH

 

ALE/ADV#

 

 

 

 

TLHLL

TLLRL

TRHLH

 

 

TRLRH

 

RD#

 

TRLDV

 

 

 

 

 

TAVLL

TRLAZ

TRHDZ

 

TLLAX

Bus Read

Address

Data In D15:0

 

AD15:0

 

 

 

 

8- and 16-bit

 

TAVDV

 

Bus Mode

 

 

 

 

TLLWL

 

 

 

TWLWH

 

WR#

 

 

 

Bus Write

 

TQVWH

TWHQX

 

 

 

AD15:0

Address Out

Data Out

 

8- and 16-bit

 

 

TWHBX, TRHBX

Bus Mode

 

 

 

 

 

BHE#

 

BHE Valid

 

 

 

 

TWHAX, TRHAX

AD15:0

AD15:8 Valid 8-bit Bus Mode

 

 

 

 

TWHIX, TRHIX

INST

 

INST Valid

 

 

 

 

A3099-01

Figure 15-23. Mode 2 System Bus Timing

15-35

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