1. MicroBaby Datapath

2. Copyright 2015 - Joanne DeGroat, ECE, OSU
MB Datapth
The MicroBaby Datapath – the main part of the processor – composed of :
The MB ALU
An accumulator
A B input, which also has a latch register to hold the value when the bus returns to high impedance, Z
Output driver to drive the bidirectional data bus.
The objective is to implement this in VHDL, verify the implementation, and then synthesize it in Quartis.
Copyright Joanne DeGroat, ECE, OSU

3. Copyright 2015 - Joanne DeGroat, ECE, OSU
The MB datapath
The datapath has the following structure
Copyright Joanne DeGroat, ECE, OSU

4. Copyright 2015 - Joanne DeGroat, ECE, OSU
Datapath components
The MB ALU
An 8-bit register for the accumulator
Ldac – load the accumulator with the value on its input
A 2-to-1x8 mux before the accumulator
Aal control signal selects between the ALU result and the databus input
A 2-to-1x8 mux before the Blatch
Bbu selects between a fixed input of “ ” and the databus input
An 8-bit register to hold the Binput to the accumulator
This is needed to prevent connection of the Binput to the ALU directly to the databus which goes back to high impedance, Z
A BusDriver
Allows the contents of the accumulator to be driven onto the bus
Copyright Joanne DeGroat, ECE, OSU

5. Control signal summary
Aal – Accumulator input selection
Bbu – B input select
Ldac – Load the accumulator (positive edge)
Dracc – Drive the accumulator value onto the databus
Bmuxlatch – Load the Blatch with data
F(3 dt 0) – the function code (ALU)
AddSub – add or subtract (ALU)
Cin – the Carry input (ALU)
Arlo – arithmetic or logic operation (ALU)
Csel – the carry input mux to the adder of the ALU
DataBus – the databus which runs on a bus cycle
Cout – the ALU carry flag
N – the ALU N flag
Z – the ALU Z flag
Copyright Joanne DeGroat, ECE, OSU

6. Copyright 2015 - Joanne DeGroat, ECE, OSU
The last step
You will be modeling each of these components, HDL simulating it, and then synthesizing it using Quartis.
A model of components will be provided along with an HDL testbench.
Copyright Joanne DeGroat, ECE, OSU

7. Copyright 2015 - Joanne DeGroat, ECE, OSU

8. Copyright 2015 - Joanne DeGroat, ECE, OSU

9. Copyright 2015 - Joanne DeGroat, ECE, OSU

10. Copyright 2015 - Joanne DeGroat, ECE, OSU