Short description
ZXblast is a memory expansion and a USB mass storage interface for the ZX81 and compatible
computers for loading and storing programs and data. It offers 128k or 512k RAM depending
on version and is configurable to enable and disable several memory areas to achieve a
maximum of 56k RAM while the first 8k is used for the ZX81 rom.
ZXblast offers additionally 128k or 512k flash rom for loading different/modified ZX81
compatible ROMs or combined with additional and/or different drivers. The 512k version allows
also to start up to 7 different programs concurrently while only the active or visible is executed
and the others are in halted state. It is possible to switch between the programs (called
instances) with simple keystrokes.
An additional feature is to activate paging with pagesize of 8k or 16k RAM with page window
anywhere in memory. This is mainly a developer feature as there was never a standard for
paging or ram banking and programs using this feature are hard to find at all.
The 128k version allows to start one instance only but with up to 56k RAM and allows to
choose between a custom ROM with additional drivers or the original internal ZX81 rom.
ZXblast has two USB ports. One is used for flash media sticks to load and store programs or
data and a second one for connecting other USB hardware like joysticks, keyboards, or similar.
This is a feature to be used in future. ZXblast has additionally a battery backuped real time
clock (RTC) to provide a correct time stamp when saving programs or datafiles. It takes it's
power from an own voltage regulator from the 9V of the ZX81 to avoid additional heat to the
internals of the ZX81.
The 128k or 512k flash ROM can be programmed with the ZXblast itself and some internal
tools. ZXblast is full compatible to HRG (high resolution graphics by software) and allows
execution of machine code (assembly) in the memory region above 32k but below 48k (called
M1NOT mod).
Technical data/specification
Flash ROM
128k or 512k
RAM
128k or 512k
USB
2 Ports
I/O address bit used
A3 (optional A4,A5,A6 or A7)
Power Supply
9V over expansion port
45 mA for ZXblast only
(plus USB devices used)
Memory configurations
16k, 24k, 32k, 40k, 48k, 56k RAM
Extras
RTC (real time clock)
paging/banking up to 448kByte
with 8k or 16k window anywhere in memory
Features
HRG high resolution graphics from memory
M1NOT (program execution >32k and <48k RAM)
V1.0 02/2017
ZXblast – user manual
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