CompuGen 3250
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CompuGen 3250 memory organization
Note that this information is for your information only. Gage’s drivers take care of all memory management
issues. As a user, or even a programmer, you do not have to worry about the details of how memory is accessed
on CompuGen 3250.
Memory architecture
The clock speeds at which the CompuGen 3250 card can generate data are too fast for the computer’s ISA bus to
handle. As such, the CompuGen 3250 has high-speed on-board memory to store the digital data from the
computer to generate waveforms.
Interface for the ISA bus
In order to allow optimum data transfer rates from the PC memory to the CompuGen memory, the on-board
memory is mapped within the memory map of the 80x86 processor, between 640K and 1M (factory default is
D200-D3FF for the CompuGen 3250).
The CompuGen 3250 takes only 4 kilobytes of memory space between 640K and 1M. This memory address is
configurable by writing to the on-board segment register, i.e. it is configured by software, not by DIP switches,
etc.
This small memory window and software configuration means that there is very little chance of memory
conflicts in any PC.
The CompuGen 3250 has memory depths much greater than just 4 KB. Therefore, the on-board memory is
addressed in a segmented manner and is divided into 4 KB blocks.
On-Board Memory Address
Block Number
0 to 4095
0
4096 to 8191
1
8192 to 12287
2
12288 to 16383
3
... ...
Using the above method, any byte of on-board memory can be addressed using the BLOCK NUMBER and an
OFFSET.
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