MA2910 Datasheet | Gec Plessey

FEATURES I Fully patible with Industry Standard 2910A I CMOS SOS Technology I Radiation Hard and High SEU Immunity I High Speed / Low Power I Fully TTL patible Figure 1: Block Diagram OPERATION The MA2910 is a SOS microprogram controller intended for use in high speed microprocessor applications. Besides the capability of sequential access, it provides conditional branching to any microinstruction within its 4096-microword range. A last-in, first-out stack provides microsubroutine return linkage and looping capability; there are nine nesting levels of microsubroutines. Microinstruction loop count control is provided with a count capacity of 4096. The device is controlled by 16, 4-bit microinstructions. The PLA decodes the microinstructions on I(3:P) and produces select control codes for the multiplexer, register/counter, microprogram counter register, and stack. The 4-bit microinstructions also generate three active low enable signals (PL, VECT, and MAP) for external use. The operation of each device block is detailed below: MULTIPLEXER The MA2910 contains a four-input multiplexer that is used to select either the register/counter, direct input, microprogram counter, or stack as the source of the next microinstruction address. REGISTER/COUNTER The register/counter consists of 12 D-type, edgetriggered flip-flops, with a mon clock enable. It is operated during microinstructions (8,9,15) as a 12-bit down counter, with result = zero available as a microinstruction branch test criterion. This provides efficient iteration of microinstructions. The register/ counter is arranged such that if it is preloaded with a number N and is then used as a loop termination counter, the...