Open Access
Expanding and Monitoring the ASB
4-6
ARM Development Board (ARM7TDMI Version)
Hardware Reference Guide
ARM DUI 0017C
4.2 Building an ASB Master Expansion Board
To build an ASB master that connects to the motherboard, you need some or all of the
signals listed in
Table 4-1: ASB signals
. The following are particularly important
A_REQ001 request to system arbiter for bus ownership
A_REQ002 request to system arbiter for bus ownership
A_GNT001 grant from system arbiter of bus ownership
A_GNT002 grant from system arbiter of bus ownership
4.2.1 Surface mount links
By default, A_REQ001 and A_REQ002 are tied LOW on the motherboard through surface
mount links. When implementing expansion bus masters, the surface mount links must be
moved to connect the arbiter request lines to the expansion header. Refer to section
3.2.19
System Modules (Arbiter and Decoder)
on page 3-24 for more information on this.
4.2.2 Interrupts
A master can issue interrupts to the system CPU through the following:
nINTASB[1:0] interrupt sources
nFIQSRC fast interrupt source
Note
An expansion master cannot receive interrupts from other devices in the system.
hrg.book Page 6 Wednesday, July 22, 1998 9:18 AM
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