[author : Tim Pugh] #Listing #Assembly #Electronic #Interface

Extract : «  There is now available a board for the S-100 BUS which, when coupled with appropriate software, can add a powerful new dimension to your system. The board I refer to is an Originate/Answer Modem board and is being produced by at least two manufacturers: D C Hayes Assoc, of Atlanta, GA and International Data Systems (IDS) of Falls Church, VA. With an Originate/Answer Modem you can implement the following functions:

1. Intelligent Terminal

2. Remote Console

3. PCNET Node

There are undoubtedly other functions which can be implemented but these three are fairly clearly defined.

The first of these functions (Intelligent Terminal) is implemented to a significant extent by the program which accompanies this article. The basic purpose of this function is to allow you to communicate with a large “Time Sharing Computer” (TSC) and effectively use the various components of your “Personal Computer” (PC) in carrying on this communication. For example, you may wish to use your video terminal for some of the communications and then switch to a printing terminal or hard copy device at the appropriate time. Also, you may wish to transfer data between the PC’s floppy disk and the TSC. [...]

The program is designed to run under CP/M and except for the I/O peculiar to the 88-Modem board, uses CP/M supplied functions to perform conventional I/O. In order to operate at a given BAUD rate it is necessary that the console device be capable of a least twice that BAUD rate. Thus, if a 30cps printing terminal is used it is necessary to operate at 150 BAUD or less. Unfortunately, this also applies to an on-line printer even if the console is a high speed video display. [...]  »

[author : Richard Emerson] #Listing #Assembly #Programming

Extract : «  There comes a point in every programmer’s life when it seems to be a good idea to store the contents of memory on a permanent medium like tape. This usually comes about two seconds after said programmer realizes that a particularly brilliant piece of code has just been clobbered by a stray glitch in memory. By then it is too late, but for those who plan ahead there is hope and AUTODUMP. This program of 1047 bytes will dump the contents of a POLY88 onto tape in either BYTE or POLYPHASE mode. That, in itself is not much, but AUTODUMP will also write a banner or comment record block of 255 characters and automatic execution of a program dumped by AUTODUMP. If you are sufficiently impressed with your handiwork, you can command AUTODUMP to produce up to 255 copies of that file. All that is required of your system is that the POLY88 USART kit be installed on the CPU card. There are three monitor subroutine references and four memory references related to the monitor. Each one will be explained in the following paragraphs. [...]  »

[author : Theodore E. Bridge] #Listing #Assembly #Storage #Book

Extract : «  This high speed cassette tape handler will load or dump at 12 times the speed of KIM-1 or twice the speed of the MICRO-ADE 1 Editor-Assembler. It replaces and overlays the editor routines CREAD and CWRITE at the end of the third 4K block of memory (2EA9-3000).

[...]

Notes

1. MICRO-ADE™ for the 6502 — Assembler, Disassembler, Editor, by Peter F. Jennings. Micro-Ware Ltd., 27 Firstbrooke Road, Toronto, Ontario, Canada, M4E 2L2.

2. The First Book of KIM, Hayden Book Co., Essex St., Rochelle Park, N.J. 07662. Cat. 5119-0. $9.00.

3. Realistic™ CTR-39, Model 14-819 by Radio Shack.

4. HELP RELAY PACKAGE, the Computerist, P.O. Box 3, S. Chelmsford, MA 01824.

5. Pyramid Data Systems, 6 Terrace Ave., New Egypt, N.J. 08533.  »

[author : U.R. Source] #Microprocessor #Review

Extract : «  Zilog’s New Z-8 is the first of a new generation of single-chip microcomputers. It is also capable of being used as an 8-bit microprocessor which can address up to 128K bytes of external memory. The architecture of the chip is such that under software control, it can be given a variety of different I/O and memory configurations, the most important of which are: a) an I/O intensive single-chip microcomputer and b) a memory intensive microprocessor with up to 64K bytes of data and 64K bytes of program memory. Such flexibility is made possible by merging the multiplexed data/address bus (and the associated control signals) with the I/O-oriented ports. Thus external memory can be addressed while as many I/O lines are needed can be maintained. [...]  »

[author : Andrew Hertzfeld] #Listing #Assembly #Programming

Extract : «  Many unfortunate souls have experienced the frustration which occurs when you realize that you have just accidentally erased the program you were working on. Kicking the computer may provide some emotional satisfaction but it won’t bring your program back. This article describes Lazarus, a short machine language program which can resurrect inadvertently erased BASIC programs on the Apple-II computer.

When an Apple-II integer BASIC program is erased, it is usually not destroyed. It is probably still sitting around somewhere in memory; however, the BASIC interpreter no longer knows where to find it so it is effectively lost. Lazarus scans through memory trying to find the largest valid BASIC program that it can. If it finds one it resets the interpreter’s pointers to point to the found program, thereby resurrecting it. If no valid program can be found an error message is printed. In either case control is returned to the BASIC interpreter. [...]  »

[author : Leor Zolman] #Listing #Assembly #BASIC #Programming #Storage #Display

Extract : «  After getting Li Chen Wang’s Tiny Basic up and running about six months ago, from the version published in Dr. Dobb’s Journal , I knew I had finally found what I had been searching for ever since first getting my IMSAI up: a well structured and documented Tiny Basic interpreter which could easily be modified to let me do my own thing. Thanks to Dr. Wang’s consideration for the needs of his Basic’s users, there was ample space available in the command and function tables to implement the extensions presented here.

The routines fall into three independent catagories: cassette tape I/O, video I/O for the Processor Technology VDM board, and a set of four routines to perform IN, OUT, PEEK, and POKE ala MITS Basic. The cassette routines are intended for use with a Tarbell Cassette Interface, but shouldn’t be too difficult to adapt to any serial storage device with a little rewriting. [...]  »