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DM93S41N Datasheet(PDF) 2 Page - Fairchild Semiconductor |
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DM93S41N Datasheet(HTML) 2 Page - Fairchild Semiconductor |
2 / 7 page www.fairchildsemi.com 2 Functional Description The DM93S41 is a 4-bit high speed parallel arithmetic logic unit (ALU). Controlled by the four Function Select inputs (S0–S3) and the Mode Control input (M), it can perform all the 16 possible operations or 16 different arithmetic opera- tions on active HIGH or active LOW operands. The Func- tion Table below lists these operations. When the Mode Control input (M) is HIGH, all internal car- ries are inhibited and the device performs logic operations on the individual bits as listed. When the Mode Control input is LOW, the carries are enabled and the device per- forms arithmetic operations on the two 4-bit words. The device incorporates full internal carry lookahead and pro- vides for either ripple carry between devices using the Cn+4 output, or for carry lookahead between packages using the signals P (Carry Propagate) and G (Carry Generate). P and G are not affected by carry in. When speed require- ments are not stringent, the DM93S41 can be used in a simple ripple carry mode by connecting the Carry output (Cn+4) signal to the Carry input (Cn) of the next unit. For super high speed operation the Schottky DM93S41 should be used in conjunction with the '42 carry lookahead circuit. The A = B output from the DM93S41 goes HIGH when all four Fn outputs are HIGH and can be used to indicate logic equivalence over four bits when the unit is in the subtract mode. The A = B output is open-collector and can be wired- AND with the other A = B outputs to give a comparison for more than four bits. The A = B signal can also be used with the Cn+4 signal to indicate A > B and A < B. The Function Table lists the arithmetic operations that are performed without a carry in. An incoming carry adds a one to each operation. Thus select code LHHL generates A minus B minus 1 (2s complement notation) without a carry in and generates A minus B when a carry is applied. Because subtraction is actually performed by complemen- tary addition (1s complement), a carry out means borrow; thus a carry is generated when there is no underflow and no carry is generated when there is underflow. As indicated the '41 can be used with either active LOW inputs producing active LOW outputs or with active HIGH inputs producing active HIGH outputs. For either case the table lists the operations that are performed to the oper- ands labeled inside the logic symbol. Function Table H = HIGH Voltage Level L = LOW Voltage Level Note 1: Each bit is shifted to the next more significant position Note 2: Arithmetic operations expressed in 2s complement notation Mode Select Active LOW Inputs Active HIGH Inputs Inputs & Outputs & Outputs Logic Arithmetic (Note 2) Logic Arithmetic (Note 2) S3 S2 S1 S0 (M = H) (M = L) (C n = L) (M = H) (M = L) (C n = H) LL LL A A minus 1 A A LL L H AB AB minus 1 A + B A + B LL H L A + B AB minus 1 ABA + B L L H H Logic 1 minus 1 Logic 0 minus 1 LH L L A + B A plus (A + B)AB A plus AB LH L H B AB plus (A + B)B (A +B) plus AB LH H L A ⊕ B A minus B minus 1 A ⊕ B A minus B minus 1 L HHH A + B A + B AB AB minus 1 HL L L ABA plus (A + B) A + B A plus AB HL L H A ⊕ B A plus B A ⊕ B A plus B HL HL B AB plus (A + B) B (A + B) plus AB HL H H A + BA + B AB AB minus 1 H H L L Logic 0 A plus A (Note 1) Logic 1 A plus A (Note 1) HH L H AB AB plus A A + B (A + B) plus A H H H L AB AB minus A A + B(A + B) plus A H H H H AA AA minus 1 |
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Similar Description - DM93S41N |
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