I

ing signal is zero. BITTIME is then obtained by individually incrementing registers Hand L. To obtain HALFBIT, divide the value of (HU' deter- mined above by two before incrementing each register.

In order to implement this algorithm, set HL to -6, verify that the incoming signal is a logic one, then wait for the start bit transition.

BP.ID: MVI A, eCeH

SIP'!

LXI H.-€H

BP.I1: RIM

ORft A

..Ip BRI!

BF'I2: RI!1

ORA A

..IM BPI2

Otherwise continue. Store HL temporarily for the HALFBIT calculation. Obtain and store BITTIME:

PUSH H

INP H

TNR L

SHLD BITTIME

Restore HL, calculate HALFBIT, and return:

pppH

ORA A

MOil ,A.H

RAP.

b10V H.H

MO',,.' A·l

PAf;'

~IO"'! L· A

WP H

Increment register pair HL, then delay so that each cycle will require 84 machine cycles:

Bf?E'

II";':

H

 

<6>

 

MYI

E. 01H

 

(7)

BRl4 '

DCR

E

"51.)

 

..TNZ

BP.I4

I

}

Check if SID is still low. If so, repeat:

PHI

 

<4>

OPR

Ii

<4}

JP

BPI::

<113)

HIP L

::HLf:o HAlJE' IT

PET

The assembled listings for these subroutines, along with a simple test program, is presented in the CRT and Cassette Code.

A1-37

Page 177 Page 179
Page 178
Image 178
Intel MCS-80/85 manual Bf?E, 01H
Page 177 Page 179

MCS-80/85 specifications

The Intel MCS-80/85 family, introduced in the late 1970s, is a seminal collection of microprocessors that played a pivotal role in the early days of computing. The MCS-80 series, initially targeting embedded systems and control applications, gained remarkable attention due to its innovative architecture and flexible programming capabilities.

The MCS-80 family is anchored by the 8080 microprocessor, which was one of the first fully integrated 8-bit microprocessors. Released in 1974, the 8080 operated at clock speeds ranging from 2 MHz to 3 MHz and featured a 16-bit address bus capable of addressing up to 64KB of memory. The processor’s instruction set included around 78 instructions, providing extensive capabilities for data manipulation, logic operations, and branching.

Complementing the 8080 was a suite of support chips, forming the MCS-80 platform. The most notable among them was the 8155, which integrated a static RAM, I/O ports, and a timer, tailored for ease of designing systems around the 8080. Other support chips included the 8085, which provided improvements with an integrated clock generator, making it compatible with more modern designs and applications.

The MCS-85 series, on the other hand, revolves around the 8085 microprocessor, which provided a more advanced architecture. The 8085 operated at clock speeds of up to 6 MHz and came with a 16-bit address bus, similar to its predecessor. However, it introduced more sophisticated features, including an enhanced instruction set and support for interrupt-driven programming. These enhancements made the 8085 especially appealing to developers working in real-time processing environments.

The MCS-80/85 family utilized NMOS technology, known for its lower power consumption and higher performance compared to previous technologies like TTL. The family’s architecture allowed for easy interfacing with a variety of peripherals, making it a favorite for educational institutions and hobbyists embarking on computer engineering projects.

With its robustness, versatility, and affordability, the Intel MCS-80/85 microprocessors laid the groundwork for many subsequent microcomputer systems and applications. The legacy of this powerful family continues to influence modern microprocessor design, emphasizing the importance of reliable architecture in a rapidly evolving technology landscape.
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