Ziatech Corporation ZT 8809A, Руководство по эксплуатации

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Memory and I/O Capability
MEMORY ADDRESSING
The ZT 8809A processor board is capable of addressing up to
1 Mbyte of memory, both on-board and to the STD bus. This is the
maximum memory addressing capability of the V20 and 8088
microprocessors. The upper four bits of the 20-bit memory address
are multiplexed onto the STD bus data lines during address time. The
remaining 16 address bits, along with memory request (MEMRQ*),
are driven onto the 16 STD bus address lines during this time. Refer
to the timing diagrams in Appendix B for timing details.
Memory Expansion (MEMEX)
The Memory Expansion (MEMEX) signal is defined in the STD-80
Series Bus Specification for use with 16-bit memory cards. The
ZT 8809A can tie this signal to Vcc or ground via jumper W60. It
does not drive this signal dynamically. Therefore, 16-bit memory
cards may not be used. Factory default ties MEMEX to ground.
On-Board Memory Capacity
Memory capacity is determined by four 32-pin JEDEC compatible
sockets. One socket is reserved for EPROMs ranging in size from
16 Kbytes through 256 Kbytes. Two other sockets are reserved for
static RAM devices ranging in size from 32 Kbytes to 512 Kbytes.
The fourth socket is configurable for RAM or EPROM. Refer to the
description of jumpers W55-59 and W67-68 in Appendix A for all of
the configurations.
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