ECE 394 - Experiment 8

ECE 394 - Experiment 8 - 1 Introduction The main purpose of...

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1 Introduction: The main purpose of this experiment is to design a 4-bit RPN calculator. Reverse Polish Notation (RPN) is a notation for representing arithmetic formulas. In this notation, the operator is placed after the two operands, for example, A B +. First, the user pushes the two values on the stack. When the user performs an operation, the RPN calculator pops the second operand from the stack, decrements the stack pointer, and store the answer in the location containing the first operand. The advantage of the RPN notation is that it eliminates the need for parentheses to determine operation precedence. There are only two possible operations the calculator can perform, Push and Function. During the Push operation, the calculator stores the value set by the X Switches into the stack. During the Function operation, the calculator performs the operation selected by the Y Switches on the top 2 values on the stack. Fig. 1 – RPN Calcuator Block Diagram Components of the RPN Calcuator block diagram: - 4x16 RAM serves as the stack of the RPN calcuator - 4-bit binary counter used as a stack pointer to choose the desired memory location on the RAM. - X Switches used to input 4-bit data values. - Y Switches used to select the function the ALU needs to perform between its A and B inputs. - MUX selects between the X Swiches and the Register 2 outputs for the RAM inputs. - ALU used to add and multiply the operands stored by the user in the RAM - Register 1 used to store second operand temporarily, while the ALU gets the first operand from the RAM to perform the desired operation - Register 2 used to store result of ALU operation temporarily until it is written to the RAM on the following clock cycle - Control unit must be able to succesfully process through the control signals needed for the RPN calculator to work. It could be implemented using a decoder or a lookup ROM. We implemented it using a lookup ROM that stores the desired control signals for each clock cycle. 1 | P a g e

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After finishing this lab, students should have successfully accomplished the following objectives: Objectives: Understand the basic structure of RPN Calculators Utilize the digital design techniques acquired in previous experiments to design a simple 4- bit RPN calculator based on the provided block diagram Design a control unit that implements the PUSH and FUNCTION functionalities of the RPN calculator. Equipment: 2 Protoboards Signal generator 1 28C16 (2K x 8) ROM 2 binary counters (74LS169D) ALU 74181 Chip 2 Shift Registers (74LS395D) XOR Gates Invertor Gates AND Gates 10 LEDs and limiting resistors 10 switches 2 Procedure: PART I – DESIGNING THE CONTROL UNIT 1 Using the ROM Programmer and the Prog-Express software, store the control signals displayed in Table 1 below on the 28C16 ROM chip using the following steps: A. Click "Modify data in a Hex-Editor" button B. Create a new file and write the data you want to it, then save the file.
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