Computer Architecture

Section 5 Solutions:

• 1. Capture the following system behavior as a High Level State Machine (HLSM). A system must track the number of times an input, T, toggles. A toggle is a change from 0 to 1 or 1 to 0. The number of toggles is tracked by a 20-bit output, C[19..0]. When a maximum number of toggles, M[19..0], is reached, the output C stops changing and holds the maximum value until the circuit is reset by the active high reset input, R.
  
  
• 2. Create a high level state machine (HLSM) for a simple data encryption/decryption device. If a single-bit input B is 1, the device stores the data from a 32-bit signed input I, referring to this as an offset value. If B is 0 and another single-bit input E is 1, then the device "encrypts" its input I by adding the stored offset value to I and outputs this encrypted value over a 32-bit signed registered output J. If both B and E are zero and another single-bit input D is 1, the device "decrypts" the data on I by subtracting the offset value before outputting the decrypted value on the output J. When not encrypting or decrypting, the value of the output J is held. Be sure to explicitly handle all possible combinations of B, E and D.
  
  A Moore solution:
  
  
  A Mealy solution:
  
  
• 3. For the given HLSM
  • A. Design a datapath circuit. Be sure to give all control signals informative names.
  • B. Design the FSM for a controller to drive the datapath.
  
  
  
  
  
  
  
• 4. For the given HLSM
  • A. Design a datapath circuit. Be sure to give all control signals informative names.
  • B. Design the FSM for a controller to drive the datapath.
  
  Inputs: Data_in (8 bits), doCalc (bit)
  Ouputs: Out (8 bit)
  Local Registers: t1 (8 bits), t2 (8 bits)