Control Logic Gates
The block diagram of the control logic gates is shown in Fig. 5-6. The inputs to this circuit come from the two decoders, the I flip-flop, and bits 0 through 11 of IR.
The other inputs to the control logic are: AC bits 0 through 15 to check if AC = 0 and to detect the sign bit in AC(15); DR bits 0 through 15 to check if DR = 0; and the values of the seven flip-flops. The outputs of the control logic circuit are:
1. Signals to control the inputs of the nine registers
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2. Signals to control the read and write inputs of memory
3, Signals to set, clear, or complement the flip-flops
4. Signals for 52, 51, and 50 to select a register for the bus
5. Signals to control the AC adder and logic circuit
The specifications for the various control signals can be obtained directly from the list of register transfer statements.