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H O M E - APOLLO181 INTRODUCTION
First Program Example
Binary Clock Algorithm
Shift-and-Add Multiplication
Prime Numbers Benchmark
PWM LED Dimmer
Step Motor Controller
Sound Generator: Part 1
Sound Generator: Part 2
Random Number Generator
EPROM Data Storage
My Previous Z80 Project

mio

 Optional Data Storage: an EPROM to retain up to 32 programs

NOTE: I am aware that the use of a 64K MOS EPROM, which was not issued before 1980, represents an anachronism during the seventies TTL Bugbook's era and in this project.

So I have dedicated this independent chapter for it, providing APOLLO181 PROCESSOR (which does remain a pure 100% TTL machine) with an optional handy non-volatile data storage. 

eprom.jpg
64K ( 8K x 8 ) EPROM which is used to retain up to 32 programs, each 256 Byte long

 

m27c64a.jpg

io27c64.jpg

mio

In 1971 Intel introduced an important invention, the Ultraviolet Erasable and Programmable Read-Only Memory (or EPROM). The Intel new EPROM 1702 could store up to two kilo bits and could retain data when the electrical power was turned off; it could even be programmed several times, while contemporary fuse-link PROM chips had only to be programmed a single time. 

EPROMs allowed the programs (used to be stored in read only memory or ROM), to be modified: that was an essential capability in the development of the microcomputer industry in the late seventies and early eighties. 

Intel introduced the industry's first EPROM in 1971 and continued to be the leader in this category of memory. In 1978 a 32K EPROM chip was released by Intel and Texas Instruments. In 1981 Intel introduced into the market the first industry's 64K unit, the 2764 EPROM.

 

Year

EPROM

Size

 

 

 

 

 

1971

1702

2Kbit

 

1975

2708

8Kbit

 

1977

2716

16Kbit

 

1978

2732

32Kbit

 

1981

2764

64Kbit

<<< 

1982

27128

128Kbit

 

1983

27256

256Kbit

 

 

apollo181eprom.jpg
APOLLO181 equipped with ZIF socket for removable EPROM to fast load programs

mio

The 2764 is a 65536 bit ultraviolet erasable and electrically programmable memory (UV EPROM). It is organized as 8192 words by 8 bits and it has 13 address pins. This memory can be easily mapped into 32 segments, each of them 256 byte long. Thus we can store in this EPROM up to 32 programs (or shorter useful algorithms, leaving blank the remanent cells), each of them up to 256 byte long, filling all the memory segments. Then we can easily select any of them, by using five switches connected to the higher address lines, A8 to A12. The remaining lower eight lines, from A0 to A7, are used to address the 256 locations in which are stored the program intructions. 

EPROM memories are a factor of three to ten times slower than bipolar RAMs, so they are used here as a bulk removable storage elements:  in less than one millisecond, with a single manual command, we copy one program or algorithm from the EPROM into APOLLO181 processor, completely filling its RAM. Furthermore, once the binary program is loaded into the RAM, we can also modify or complete it, by using the data and address binary switches on the APOLLO181 board. Then we can let APOLLO181 processor run at the maximum frequency (3 MHz) that program, which is now resident in the much faster TTL bipolar memory. Of course any modification done under APOLLO181 will be lost as soon as we turn the power off. 

By adopting a Zero Insertion Force (ZIF) 28 pin socket, we can also easily remove the EPROM and substitute it with a similar one containing other different additional 32 programs.

7403nand.jpg
7403 open-collector NANDs connected to the data switches to implement active-low wired-OR

mio

 

EPROM MEMORY MAPPING in APOLLO181

 

 

 

 

 

 

 

 

 

Dip-Switch

Hex Address

Size (byte)

Program No

 

Dip-Switch

Hex Address

Size (byte)

Program No

 

 

 

 

 

 

 

 

 

00000 (00)

0000-00FF

256

Program N°1

 

10000 (10)

1000-10FF

256

Program N°17

00001 (01)

0100-01FF

256

Program N°2

 

10001 (11)

1100-11FF

256

Program N°18

00010 (02)

0200-02FF

256

Program N°3

 

10010 (12)

1200-12FF

256

Program N°19

00011 (03)

0300-03FF

256

Program N°4

 

10011 (13)

1300-13FF

256

Program N°20

00100 (04)

0400-04FF

256

Program N°5

 

10100 (14)

1400-14FF

256

Program N°21

00101 (05)

0500-05FF

256

Program N°6

 

10101 (15)

1500-15FF

256

Program N°22

00110 (06)

0600-06FF

256

Program N°7

 

10110 (16)

1600-16FF

256

Program N°23

00111 (07)

0700-07FF

256

Program N°8

 

10111 (17)

1700-17FF

256

Program N°24

01000 (08)

0800-08FF

256

Program N°9

 

11000 (18)

1800-18FF

256

Program N°25

01001 (09)

0900-09FF

256

Program N°10

 

11001 (19)

1900-19FF

256

Program N°26

01010 (0A)

0A00-0AFF

256

Program N°11

 

11010 (1A)

1A00-1AFF

256

Program N°27

01011 (0B)

0B00-0BFF

256

Program N°12

 

11011 (1B)

1B00-1BFF

256

Program N°28

01100 (0C)

0C00-0CFF

256

Program N°13

 

11100 (1C)

1C00-1CFF

256

Program N°29

01101 (0D)

0D00-0DFF

256

Program N°14

 

11101 (1D)

1D00-1DFF

256

Program N°30

01110 (0E)

0E00-0EFF

256

Program N°15

 

11110 (1E)

1E00-1EFF

256

Program N°31

01111 (0F)

0F00-0FFF

256

Program N°16

 

11111 (1F)

1F00-1FFF

256

Program N°32

apollo181plusz80.jpg
APOLLO181 and Z80/AM95 8-bit NANO COMPUTER here used as EPROM burner machine

mio

As EPROM programmer, I'm using my Z80/AM95 8-bit NANO COMPUTER, which is equipped with an on-board Eprom/EEprom burner .

Of course, I tested that APOLLO181's Data Storage works very well also with EEPROM (or E2PROM, Electrically Erasable Programmable Read-Only Memory), much easier to write and cancel when performing algorithm tests. The first EEPROM was designed in 1983 by Intel and it was a 16Kbit chip.

epromeraser.jpg
Helios Italquartz EPROM eraser: EPROMs are normally erased by UV in the UVC range

DISCLAIMER & CREDIT: All data here reproduced are for educational and non-commercial purpose, following fair-use guidelines.

This is an INDIPENDENT AND UNOFFICIAL hobby site. Either Dr. Peter R. Rony or the Blacksburg group or Computer History Museum (Mountain View, CA) or other third-party DO NOT HAVE ANY ASSOTIATION with this work.

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Text and images from original typewritten Bugbooks I and II in 1974 are permission courtesy of Dr. Peter R. Rony, the original author and sole copyright owner of the Bugbooks I, II, IIA, III, V, and VI.

The background image on the header of each page of the site is "Sunset over western South America" photographed on 12 April 2011 by an Expedition 27 crew member on the International Space Station. (Image credit: NASA). On it I have merged titles and a my photo of TIL302 displays.

Texas Instruments data are Texas Instruments Copyright and reported by Courtesy of Texas Instruments.

 

TERM OF USE: With clear exception for texts and images which are not author's property, Gianluca G. freely authorizes you the downloading, printing and reproducing of APOLLO181 data, texts and images ONLY for non-commercial usage and ONLY if you give a clear reference to its source and project namewithout any right to resell or redistribute them or to compile or create derivative works.

Any rights not expressly granted herein are reserved.

 

Copyright (c) 2012 by Gianluca G. Italy