Am2901
4-bit ALU from the Am2900 series of processor chips. Similar functionality to 74181 or i3002 / MH3002.
Manufactured in the USSR under the designation KM1804VS1.
0 0 0 ADD R Plus S R ⊕ S ⊕ Carry 0 0 1 SUBR S Minus R R' ⊕ S ⊕ Carry 0 1 0 SUBS R Minus S R ⊕ S' ⊕ Carry 0 1 1 OR R OR S (R' ∧ S') ⊕ 1 1 0 0 AND R AND S R ∧ S 1 0 1 NOTRS R' AND S R' ∧ S 1 1 0 EXOR R EX OR S R ⊕ S' ⊕ 1 1 1 1 EXNOR R EX NOR S R' ⊕ S' ⊕ 1
- Data Input Pins:
- ''A0–A3'': Address inputs for selecting one of the 16 registers for operand A.
- . B0–B3'': Address inputs for selecting one of the 16 registers for operand B.
- ''D0–D3'': External data input to be written into the register file or used in ALU operations.
- Data Output Pins
- Y0–Y3: Output of the ALU result.
- F0,F3: ALU result output.
- Control Inputs
- I0–I8: Instruction inputs to control the operation mode of the ALU.
- I0–I2: Register and data source control.
- I3–I5: ALU function control.
- I6–I8: Destination control.
- ''OE#'': Output Enable for Y outputs.
- ''CN'': Carry input to the ALU.
- ''CLK'': Clock input for synchronous operations.
- Status Outputs:
- CN4: Carry output from the ALU.
- G (Generate): Used for carry generation in cascaded configurations.
- P (Propagate): Used for carry propagation in cascaded configurations.
- OVR (Overflow): Indicates arithmetic overflow during operations.
- ZERO: Indicates all bits of the ALU result are zero.
To cascade multiple AM2901 chips to create wider word widths (e.g., 8, 16, or 32 bits):
* Carry Propagation:
- Connect `CN4` (carry-out) of the lower-order chip to `CN` (carry-in) of the next higher-order chip.
- Use `G` (generate) and `P` (propagate) signals to manage carry lookahead logic for faster operation.
2. Control and Addressing:
- Share `A`, `B`, `D`, and `I` control lines across all chips in the cascade.
- Ensure `CLK`, `OE`, and other control signals are shared.
3. Output Connections:
- Combine the `Y` or `F` outputs of all chips to form the complete result.
- Ensure proper tri-state bus handling for shared outputs.
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