Introduction
Devices that can be used in the ZT 8825 include: EPROMs (for
example, 27128, 27256, 27512, 27010, 27020, 27040, up to 1 Mbyte
chips), 5V-only EEPROMs (for example, 28C256, 28C010), and
static RAMs (for example, HM62256, HM628128). The maximum
amount of memory on a ZT 8825 is limited to 2 Mbytes. There are
also some limitations to the combinations of chip sizes that can be
used (see page 3-5).
The STD-80 Series 20-bit memory address protocol is used for
memory addressing. The board will also accept 24-bit addressing.
The on-board registers use 8- or 16-bit I/O addresses. The ZT 8825
configured with 120 ns memories operates without wait states when
used with an 8 MHz processor board such as the ZT 8809. The
ZT 8825 configured with 250 ns memories operates without wait
states when used with a 5 MHz CPU board. An optional wait state is
user-selectable, allowing the use of slower memory devices (see page
3-6).
An example of the versatility of the ZT 8825 is that EPROM can be
used on one half of the ZT 8825 and RAM on the other half. This
arrangement will provide the total memory requirements for many
STD systems. The ZT 8825 is effectively two byte-wide boards in
one. See Chapter 4 for details on additional application examples.
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