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ASP.NET code-128c DATAPATH AND CONTROL in .NET Generator pdf417 in .NET DATAPATH AND CONTROL

DATAPATH AND CONTROL use none none implementation torender none on nonecode 128 generator asp.net Preamble Postnet MODULE: MOD_4_COUNTER. INP UTS: x. OUTPUTS: Z[2].

MEMORY: 0: Z 0,0; GOTO {0 CONDITIONED 1 CONDITIONED 1: Z 0,1; GOTO {0 CONDITIONED 2 CONDITIONED 2: Z 1,0; GOTO {0 CONDITIONED 3 CONDITIONED 3: Z 1,1; GOTO 0. END SEQUENCE. END MOD_4_COUNTER.

. ON x, ON x}. ON x, ON x}. none for none ON x, ON x}.

. Statements Epilogue Figure 6-20. HDL sequence for a resettable modulo 4 counter. MOD_4_COUNTER closes the description of the module. Anything that appears between END SEQUENCE and END MOD_4_COUNTER occurs continuously,. independent of the stateme none for none nt number. There are no such statements for this case. In translating an HDL description into a design, the process can be decomposed into separate parts for the control section and the data section.

The control section deals with how transitions are made from one statement to another. The data section deals with producing outputs and changing the values of any memory elements. We consider the control section rst.

There are four numbered statements, and so we will use four ip- ops, one for each statement, as illustrated in Figure 6-21. This is referred to as a one-hot encoding approach, because exactly one ip- op holds a true value at any time. Although four states can be encoded using only two ip- ops, studies have shown that the one-hot encoding approach results in approximately the same circuit area when compared with a more densely encoded approach; but more importantly, the complexity of the transfers from one state to the next are generally simpler and can be implemented with shallow combinational logic circuits, which means that the clock rate can be faster for a one-hot encoding approach than for a densely encoded approach.

In designing the control section, we rst draw the ip- ops, apply labels as. DATAPATH AND CONTROL Z[0]. DATA SECTION CONTROL SECTION Z[1]. D Q 0 CLK D Q 1 D Q 2 D Q 3 Figure 6-21. Logic design for a modulo 4 counter described in HDL. appropriate, and connect t he clock inputs. The next step is to simply scan the numbered statements in order and add logic as appropriate for the transitions. From statement 0, there are two possible transitions to statements 0 or 1, conditioned on x or its complement, respectively.

The output of ip- op 0 is thus connected to the inputs of ip- ops 0 and 1, through AND gates that take the value of the x input into account. Note that the AND gate into ip- op 1 has a circle at one of its inputs, which is a simpli ed notation that means x is complemented by an inverter before entering the AND gate. A similar arrangement of logic gates is applied for statements 1 and 2, and no logic is needed at the output of ip- op 3 because statement 3 returns to statement 1 unconditionally.

The control section is now complete and can execute correctly on its own. No outputs are produced, however, until the data section is implemented. We now consider the design of the data section, which is trivial for this case.

Both bits of the output Z change in every statement, and so there is no need to condition the generation of an output on the state. We only need to produce the correct output values for each of the statements. The least signi cant bit of Z is true in statements 1 and 3, and so the outputs of the corresponding control ip- ops are ORed to produce Z[0].

the most signi cant bit of Z is true in statements 2 and 3, and so the outputs of the corresponding control ip- ops are ORed to produce Z[1]. The entire circuit for the mod 4 counter is now complete, as shown in Figure 6-21..

DATAPATH AND CONTROL We can now use our HDL in describing the control section of the ARC microarchitecture. There is no need to design the data section, since we have already de ned its form in Figure 6-10. The data section is the same for both the microcoded and hardwired approaches.

As for the microcoded approach, the operations that take place for a hardwired approach are: 1) Fetch the next instruction to be executed from memory. 2) Decode the opcode. 3) Read operand(s) from main memory or registers, if any.

4) Execute the instruction and store results. 5) Go to Step 1. The microcode of Figure 6-15 can serve as a guide for what needs to be done.

The rst step is to fetch the next user-level instruction from main memory. The following HDL line describes this operation:.
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