Microcomputer controller and direct memory access apparatus ther

Details Microcomputer controller and direct memory access apparatus ther Microcomputer controller and direct memory access apparatus ther

1977-05-23

1978-10-24

Chapnick, Melvin B.

Boots, shoes, and leggings

G06F 1300

Patent

active

041225201

ABSTRACT:
A microcomputer controller for a printer, and apparatus for facilitating direct memory access to the microcomputer, includes a central processing unit (CPU) with a known set-up time at the beginning of each machine cycle. A memory, associated with the CPU, has an access time less than the CPU set-up time. A pair of three-state buffers are utilized on the address bus to, and the data bus to and from, the memory from each of the CPU and a direct memory access (DMA) port. A DMA control circuit is coupled to the three-state buffers to facilitate direct access to the memory, from the DMA port, during CPU set-up time intervals and also returns control of memory access to the CPU when the set-up, or synchronization, time interval ends. The microcomputer controller is utilized with additional memory, of the read-only type, and shift registers for realizing a printer controller capable of receiving print character data from the DMA port and causing that data to be printed as the associated symbol, indicia and the like, in a print font selected responsive to incoming data.

REFERENCES:
patent: 3931613 (1976-01-01), Gruner et al.
patent: 3934227 (1976-01-01), Worst
patent: 3986170 (1976-10-01), Valassis et al.
patent: 4016541 (1977-04-01), Delagi et al.
patent: 4024506 (1977-05-01), Spaargaren
patent: 4047157 (1977-09-01), Jenkins
patent: 4056848 (1977-11-01), Gilley

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