AMMC002AWP datasheet(9/39 Pages) AMD

9 / 39 page

AmMC0XXA

PREL I M I N AR Y

Data Accesses

The Miniature Card has a 16-bit data bus that can

accommodate word or byte accesses. By individually

asserting CEL# and CEH#, a host can access either

byte. However, byte swapping (moving the high byte

data to the low byte) is not supported.

Figure 2 shows the connections between the host and

Miniature Card. The host system address lines range

from A0-A25, whereas the Miniature Card address

lines range from A0–A24. On the host, A0 and the

byte/word line are sent to a decoder and output to

CEL# and CEH# on the Miniature Card. These two bits

enable a single device for byte accesses and two

devices for word accesses, as shown by the decoder

truth table in Figure 2. Again, the Miniature Card

address lines do not receive input from host address bit

A0. In this document, all address references are card

addresses, unless otherwise noted. Table 4 shows the

read/write modes for Miniature Cards.

Not connected on 2 Mbyte card

** Not connected on 2 and 4 Mbyte card

*** Not connected

Figure 2.

Host/Card Address Connections

Host

Byte/Word

A25

Card

CEH#

CEL#

A24

A23***

A24***

A23

A22***

A22

A21**

60-Pad Connector

Decoder

Decoder Truth Table

Input

Output

B/W

CEL

CEH#

0000

0101

1000

1110

20975D-3

Host Bus

Card Bus

A21

A20*

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