Specifications

Acorn Enhanced Expansion Card Specification
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Contents
Acorn Enhanced Expansion Card
Introduction 1
DEBI 1
Acorn expansion bus 1
Physical dimensions 1
Types of expansion card 2
Acorn machine range I/O type inclusions 2
System architecture 3
Expansion card access speed 3
Expansion card size 3
Data bus mapping 4
Expansion card interrupt handling 4
Expansion card interrupt mask register 5
Expansion card interrupt status register 5
Layout and drive 5
Heating 5
Expansion card identity 6
Expansion card identity space 6
Code space 6
Expansion card identity low byte 6
Expansion card presence 6
Expansion card interrupts 6
ID field 7
Conformance bit 7
Identification extension 7
FIQ and IRQ status 7
Country code 7
Manufacturer’s code 8
Product type code 8
Interrupt status pointers 8
Chunk directory structure 8
Operating system identity byte 9
Examples of use 9
IOC expansion cards 10
Expansion card accesses 12
MEMC expansion cards 18
I/O controller interface 18
MEMC expansion card timing 21
The Acorn enhanced expansion bus backplane pin-out 21
I
2
C bus 21
Reset 21
Power consumption 21