ECE 394 - Experiment 7 - 1 Introduction The purpose of this...

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1. Introduction: The purpose of this experiment is to understand the basic structure and operation of 2 electronic circuit components, the Random Access Memory and Arithmetic Logic Unit. The Random Access Memory (RAM) used for this experiment is the 16 x 4 RAM, 7489 chip. This chip can store 16 words of 4 bits each. The enable signal (ME) of the 7489 chip is active low; if the ME signal is connected to High voltage level, the four outputs of the RAM chip become at high impedance level and the chip becomes disabled. Moreover, the Write Signal (WE) is also active low. Hence, the WE signal can be used to store data to the RAM when connected to Low voltage level, or just read the data when connected to High Level. One of the most important measurements used in RAM operations is: Memory Access Time is the time taken by the RAM hardware to show the data stored in the selected memory location after the user had selected the appropriate address bits and asserted the memory enable signal. The access time represents how fast the memory can respond to data requests. It can be easily measured by determining the time difference between the rising edge in one of the Address bits and the rising edge on the corresponding Data bit. The Arithmetic Logic Unit (ALU) used in this experiment is the 74181 chip. The ALU is the kernel block of a central processing unit (CPU) because it can perform different kinds of arithmetic operations such as addition and subtraction. The 74181 has parallel full adder and subtractor circuits and it can perform 16 different arithmetic operations; it can also perform 16 logic operations, which we are not interested in using for this experiment. Objectives: Become familiar with the structure and the basics mechanism of the random access memory (RAM) circuit. Gain experience with reading, data fetching, and writing, data loading, to the RAM. Measure the 7489 chip memory access time. Understand the basic operation of the ALU chip and how to use its various functions Equipment: Protoboard Oscilloscope Signal generator 2 TTL 32x4 RAM (7489) 1 TTL binary counter (7493) ALU 74181 Chip 8 LEDs and limiting resistors 6 switches 2. Procedure: 1 | P a g e
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PART I – TESTING RAM 1. Find the 7489 chip – 16 x 4 RAM, 7493 chip – binary counter, 4 switches, 8 LEDs and 8 resistors in the electronics kit. Then, use Figures 1 & 2 to assign the ME and WE signals to the correct Logic values and connect the input switches and output LEDs to the correct pins. 2. Connect the address pins to the 7493 binary counter chip according to the diagram in Figure 3. Note that the 7493-chip pin configuration schematic is attached in Figure 4 below. 3. Afterwards, Hardwire the ME signal to Ground and the WE to a switch. Verify the write and read operations by storing a few binary data words into the memory using the 4 input switches when WE switch is Low and reading the input data when WE switch is connected to High.
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