The imm6-26 Card uses Intel 1702A Programmable Read-Only Memory chips as its storage medium. These chips represent a considerable advance in the field of read-only memory, as they can be erased and reprogrammed as the need arises. This capability makes the imm6-26 Card a valuable addition to a system in which the stored data is occasionally subject to change, for example, during the development of mask-programmed read-only memory. The imm6-26 PROM Card can be used to store programs in final stages of correction, before the program is well enough defined to justify the expense of creating masks. Also, the imm6-26 PROM Card can be used instead of read-only memory in preproduction equipment that may have to be shipped before mask-programmed read-only memory is available.
More than one imm6-26 Card may be used in a system. For example, the imm6-82 Central Processor Card can address up to 16,384 words of memory on four separate imm8-26 cards. The imm6-26 Card may also be used in parallel with an imm6-28 Random Access Memory Card.
The Functional Units
In order to describe its operation, the imm6-26 Card has been divided into four functional units:
1. The Address Control Block, which determines which card is to be used for a memory operation, and which memory location on that card is being addressed.
2. The Operation Control Block, which cpntrols the execution of all operations performed by the card.
3. The Memory Data Buffer, which buffers the data being read from memory.
4. The Memory Block, which contains the actual memory components.
