SCHOTTKY BIPOLAR 8212

VIII. 8008 System

This shows the 8212 used in an 8008 microcomputer system. They are used to multiplex the data from three different sources onto the 8008 input data bus. The three sources of data are: memory data, input data, and the interrupt instruction. The 8212 is also used as the uni-directional bus driver to provide a proper drive to the address latches (both low order and high order are also 8212's)and to provide ade- quate drive to the output data bus. The control of these six 8212'sin the 8008 system is provided by the control logic and clock generator circuits. These circuits consist of flip-flops, decoders, and gates to generate the control functions necessary for 8008 microcomputer systems. Also note that the input data port has a strobe input. This allows the proces-

sor to be interrupted from the input port directly. The control of the input bus consists of the data bus input signal, control logic, and the appropriate status signal for bus discipline whether memory read, input, or interrupt acknowledge. The combina- tion of these four signals determines which one of these three devices will have access to the input data bus. The bus driver, which is implemented in an 8212, is also controlled by the control logic and clock generator so it can be 3-statedwhen neces- sary and also as a control transmission device to the address latches. Note: The address latches can be 3-statedfor DMA purposes and they provide 15 miHi amps drive, sufficient for large bus systems.

8008 SYSTEM

INPUT

BUS

ADDRESS

DATA

DRIVER

BUS

 

LATCHES

MEMORY

 

LOW ORDER

 

(8 BITS)

DATA

 

 

 

INPUT

 

 

 

------ vee

 

STROBE

 

 

 

 

 

 

00-07

 

 

 

 

INPUT

SYNC

 

 

 

HIGH ORDER

DATA

 

 

 

(6 BITS)

 

INT

 

 

 

 

 

READY ~

 

 

 

¢1

¢2

I

 

 

 

 

t

l

 

 

 

L-..----......----0111 MEM READ

I

••••••

DATA BUS

 

OUT

"""--'----------4----rJIIIINPUT(04,5,6,7)

--------- 4 ----- oIIIINT ACK I

-----...... ----- tlDATA BUS IN b --------- ..WR

INTERRUPT

8212

' - f -- I ------------ . q,NTREO.

I

.. OUT

INSTRUCTION

 

WAIT REQ.------l.MI

I

 

 

 

'-

J

 

CONTROL LOGIC & CLOCK GEN.

5-106

Page 173 Page 175
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Image 174
Intel 8080 manual Viii System, Out, Vee, MEM Read
Page 173 Page 175

8080 specifications

The Intel 8085 and 8080 microprocessors were groundbreaking innovations in the world of computing, paving the way for future microprocessor development and personal computing.

The Intel 8080, introduced in 1974, was an 8-bit microprocessor that played a fundamental role in the early days of personal computing. With a 16-bit address bus, it had the capability to address 64 KB of memory. Running at clock speeds of 2 MHz, the 8080 was notable for its instruction set, which included 78 instructions and 246 opcodes. It supported a range of addressing modes including direct, indirect, and register addressing. The 8080 was compatible with a variety of peripherals and played a crucial role in the development of many early computers.

The microprocessor's architecture was based on a simple and efficient design, making it accessible for hobbyists and engineers alike. It included an 8-bit accumulator, which allowed for data manipulation and storage during processing. Additionally, the 8080 featured registers like the program counter and stack pointer, which facilitated program flow control and data management. Its ability to handle interrupts also made it suitable for multitasking applications.

The Intel 8085, introduced in 1976, was an enhancement of the 8080 microprocessor. It maintained a similar architecture but included several key improvements. Notably, the 8085 had a built-in clock oscillator, simplifying system design by eliminating the need for external clock circuitry. It also featured a 5-bit control signal for status line management, which allowed for more flexible interfacing with peripheral devices. The 8085 was capable of running at speeds of up to 3 MHz and had an extended instruction set with 74 instructions.

One of the standout features of the 8085 was its support for 5 extra instructions for stack manipulation and I/O operations, which optimized the programming process. Additionally, it supported serial communication, making it suitable for interfacing with external devices. Its 16-bit address bus retained the 64 KB memory addressing capability of its predecessor.

Both the 8080 and 8085 microprocessors laid the groundwork for more advanced microprocessors in the years that followed. They demonstrated the potential of integrated circuits in computing and influenced the design and architecture of subsequent Intel microprocessors. Their legacy endures in the way they revolutionized computing, making technology accessible to a broader audience, and their influence is still felt in the design and architecture of modern microprocessors today.
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