Electronics Technology Digital Electronics Electronics Technology Landon Johnson MEMORY DEVICES

Memory Competencies 67. Given a memory chip part number the student will state how many words it can hold with 100% accuracy. 68. Given a memory chip part number the student will state how large each word is that can be contained in this chip with 100% accuracy. 69. Given a memory chip part number the student will state how many address lines are needed to access these words with 100% accuracy. 70. Given a memory chip part number the student will state how many bits the chip can hold with 100% accuracy.

Memory Vocabulary MASS MEMEORY- auxiliary memory; store large amounts of data external to computer’s internal memory (e.g. magnetic tape, magnetic or optical disc) INTERNAL MEMORY- computer’s main memory; semiconductor devices; stores instructions and data currently working on. MEMORY CELL- device or circuit used to store one bit. MEMORY WORD- group of bits representing instructions of data; normally eight bits (BYTE); can range from four to sixty-four bits. CAPACITY- number of bits stored in a device; 4K X 8 = 4 X 1024 X 8 = 32,768 bits. ADDRESS- number that identifies the location of a word in memory. READ OPERATION- word stored at an address is sensed and transferred to another device (aka FETCH) WRITE OPERATION- a new word is placed in a particular memory location.

General Memory Operation 32 X 4 MEANS 32 WORDS EACH CONTAINING 4 BITS. 32 STORAGE LOCATIONS REQUIRE 5 ADDRESS LINES 00000 TO 11111 (0 -31) MEMORY CAPACITY = 32 WORDS OF 4 BITS EACH = 32 X 4 = 128 BITS

TEST How many words can this memory hold? 4 X 1024 = 4096 words *NOTE 1K = 1024 How many words can this memory hold? 4 X 1024 = 4096 words How large is each word in this memory? 8-bit words How many address lines are needed to access each word location? 12 How many bits can this memory hold? 4096 words X 8-bits/word = 32, 768

Memory Competencies 71. Without references, the student will state what the acronym RAM stands for with 100% accuracy. 72. Without references, the student will state what the acronym RWM stands for with 100% accuracy. 73. Without references, the student will state what the acronym ROM stands for with 100% accuracy. 74. Without references, the student will state what the acronym PROM stands for with 100% accuracy. 75. Without references, the student will state what the acronym EPROM stands for with 100% accuracy. 76. Without references, the student will state what the acronym EEPROM stands for with 100% accuracy.

Memory Vocabulary VOLATILE MEMORY- memory is lost if power goes off. RANDOM ACCESS MEMORY (RAM)- device where location of memory has no effect on read or write time. SEQUENTIAL ACCESS MEMORY (SAM)- memory access time varies according to address location (e.g. magnetic tape) READ/WRITE MEMORY (RWM)- any memory that can be read from or written to with equal ease. READ ONLY MEMORY (ROM)- device which is read more often than written; true ROM written once at the factory. PROGRAMMABLE READ ONLY MEMORY (PROM)- ROM that can be electrically programmed by the user; cannot be erased or reprogrammed. ELECTRICALLY PROGRAMMABLE READ ONLY MEMORY (EPROM)- ROM that can be electrically programmed by the user. It can be erased (usually with ultra-violet light) and reprogrammed as often as desired. ELECTRONICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM)- ROM that can be electrically programmed, erased and reprogrammed.

Microcomputer system block diagram Input ports The input ports connect to devices such as keyboards The address bus is unidirectional The data bus is bidirectional MPU The MPU is the heart of the system ROM The ROM contains programs and permanent data The control bus is unidirectional RAM The RAM contains temporary data (and programs) Output ports The output ports connect to devices such as printers

OVERVIEW OF MEMORY (Cont’d.) Categories of Semiconductor Storage Cells: SRAM (static random-access memory) DRAM (dynamic random-access memory) ROM (read-only memory) EPROM (electrically programmable ROM) EEPROM (electrically erasable PROM) Flash Memory See next slide for characteristics of each category of memory.

RANDOM-ACCESS MEMORY (RAM) Characteristics of RAM: Data can be “written” to RAM Stored data can be “read” at any time Volatile - cannot be used for permanent memory Access to any memory location (address) at any moment Types of RAM: SRAM (static RAM) - stores data in flip-flop-like cells. Holds 0 or 1 as long as IC has power (volatile). DRAM (dynamic RAM) - memory cells need refreshing many times per second. Also volatile.

READ-ONLY MEMORY (ROM) Characteristics of ROM: Non-volatile - memory is not lost when power is turned off Data is stored permanently Data stored in ROM can be “read” at any time ROM cannot be reprogrammed High density

PROGRAMMABLE READ-ONLY MEMORY (PROM) Data can be programmed or “burned” into a PROM Mask-programmable ROM (usually simply called ROM) Field-programmable ROM (PROM) Erasable programmable ROM (EPROM) Electrically erasable PROM (EEPROM or E2PROM) Flash EEPROM Types of PROM:

Memory Competencies 71. Without references, the student will state what the acronym RAM stands for with 100% accuracy. 72. Without references, the student will state what the acronym RWM stands for with 100% accuracy. 73. Without references, the student will state what the acronym ROM stands for with 100% accuracy. 74. Without references, the student will state what the acronym PROM stands for with 100% accuracy. 75. Without references, the student will state what the acronym EPROM stands for with 100% accuracy. 76. Without references, the student will state what the acronym EEPROM stands for with 100% accuracy.