Decoder, Enable Gate, System | Intel 8080 specs

SCHOTTKY BIPOLAR 8205

FUNCTIONAL DESCRIPTION

Decoder

The 8205 contains a one out of eight binary decoder. It ac- cepts a three bit binary code and by gating this input, creates an exclusive output that represents the value of the input code.

For example, if a binary code of 101 was present on the AO, A1 and A2 address input lines, and the device was enabled, an active low signal would appear on the 05 output line. Note that all of the other output pins are sitting at a logic high, thus the decoded output is said to be exclusive. The decoders outputs will follow the truth table shown below in the same manner for all other input variations.

Enable Gate

		~
.		I""
		l -
		I""
.		I-.
.		I""
		....
	DECODER	-
	DECODER	-
		-
		....
		l -
		I""
		-
		....
		.......

When using a decoder it is often necessary to gate the out-
puts with timing or enabling signals so that the exclusive
output of the decoded value is synchronous with the overall		ENABLE GATE
system.			--_"I "'		(E'i·"E2·E3)
			.!......I
The 8205 has a bu itt-in function for such gating. The three
enable inputs (E 1, E2, E3) are ANDed together and create
a single enable signal for the decoder. The combination of
both active "high" and active "Iow" device enable inputs
provides the designer with a powerfully flexible gating func-
tion to help reduce package count in his system.			ENABLE		OUTPUTS
ADDRESS			ENABLE		OUTPUTS
A o A, A 2		E, E2		E3 0	1 2 3 4	5 6 7
L L	L	L L H L H H H H H H H
H L	L	L	L	H H L H H H H H H
L H L		L L H H H L H H H H H
H H L L L H H H H L H						H H H
L L H L			L	H H H H H L		H H H
H L	H L L			H H H H H H L H H

L H H L L H H H H H H H L H

H H H L L H H H H H H H H L

X X X L L L H H H H H H H H

X X X H L L H H H H H H H H

X X X L H L H H H H H H H H

X X X H H L H H H H H H H H

X X X H L H H H H H H H H H

X X X L H H H H H H H H H H

X X X H H H· H H H H H H H H

5-148

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.

Intel 8080 manual Decoder, Enable Gate, System

Models: 8080

SCHOTTKY BIPOLAR 8205

FUNCTIONAL DESCRIPTION

Decoder

Enable Gate

system.

OUTPUTS

8080 specifications