ARM ARM7TDMI - Page 41

Open Access
Circuit Descriptions
3-25
ARM Development Board (ARM7TDMI Version)
Hardware Reference Guide
ARM DUI 0017C
3.2.20 ASB Expansion Connectors
The ASB expansion connectors schematic is shown in A.22 ASB Expansion Connecters
on page A-23.
This schematic shows six 20-way box headers (POD7–12) which can be used to expand or
monitor the ASB.
For expansion devices there are three interrupt pins available nINTASB[1:0] and nFIQSRC.
These are all active LOW inputs to the interrupt controller, with on-board pull-up resistors.
Note however that nFIQSRC is also connected to the APB expansion connectors, so in
order to share the signal line make drivers open-collector. To select external devices two
signals D_SELASB[1:0] are available. To enable these lines drive the signals nENASB[1:0]
LOW.
If you are planning to build external expansion devices for the ASB, refer to
Chapter 4,
Expanding and Monitoring the ASB
for further details.
hrg.book Page 25 Wednesday, July 22, 1998 9:18 AM