Chapter 3. STD Bus Interface
29
is also used to pull up the EA control signals that are open collector. Only one master in the system
can provide these pullups. Normally, RP1 will be removed when configured as a temporary master
(RP2 and RP3 removed). If another CPU type that is SA only (for example, ZT 8901, ZT 8902,
ZT 8903, ZT 8904) is configured as a permanent master, then one ZT 8905 must have RP1
installed to provide the pull-up feature for the STD 32 backplane. If two or more ZT 8905s are
being used as temporary masters to one 16-bit board (e.g. ZT 8902), then only one of the ZT 8905
temporary masters can have RP1 installed.
•
An STD 32 backplane is required.
•
A ZT 89CT39, ZT 8911 (CPU/arbiter), or equivalent bus arbiter is needed to manage ZT 8905
access to the STD bus resources. If the ZT 89CT39 is used, it must be Revision D or higher.
•
If a local PCI VGA interface is not used in multiple master operation and an STD 32 shared VGA is
used, a ZT 96048 emulation RAM must be loaded in socket T6C (shown below) to retain video
memory when the ZT 8905 is switched away from the backplane VGA device.
ZT8905F3-06
pentium
TM
A
B
C
D
E
F
W1
SOCKET T6C
Socket T6C Location
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