Specifications

CHAPTER 3
Expansion
The PDS Expansion Card 35
restrictions for the expansion card. Foldout 3 shows how the card is installed on the main
logic board.
Expansion Card Connectors 3
The custom 114-pin PDS connector on the computer’s main logic board accepts either a
96-pin or 120-pin standard Euro-DIN connector. You can order connectors meeting Apple
specifications from Amp Incorporated, Harrisburg, PA 17105 or from Augat
Incorporated, Interconnect Products Division, P. O. Box 779, Attleboro, MA 02703. Refer
to Designing Cards and Drivers for the Macintosh Family, third edition, for more information
about those connectors.
Address Space for the Expansion Card 3
The expansion card’s address space depends on the memory addressing mode. In 24-bit
mode, the card appears in the address space $E0 0000–$EF FFFF; in 32-bit mode, the card
appears in the address space $8000 0000–$FFFF FFFF. To match the conventions used by
the Slot Manager, software should address the card as if it were in slot space $E: either
the 16 MB slot space $FE00 0000–$FEFF FFFF or the super slot space
$E000 0000–$EFFF FFFF.
The expansion card must generate its own select signal from the address and function
code signals on the connector. The card select signal must be disabled when FC0, FC1,
and FC2 are all active; that condition corresponds to a function code of 111 (CPU space).
Figure 3-1 shows a typical logic circuit for generating the card select signal.
Figure 3-1 Generating the card select signal
IMPORTANT
To ensure compatibility with future hardware and software, you should
minimize the chance of address conflicts by decoding all the address bits.
To ensure that the Slot Manager recognizes your card, the card’s
declaration ROM must reside at the upper address limit of the 16 MB
address space ($FE00 0000–$FEFF FFFF). ▲
A31
FC0
FC1
FC2
FC3
A23
A22
A21
A20
Card
select
32-bit mode
select
24-bit mode
select
Disable selection
on interrupt
acknowledge
cycles