Questions tagged [io]

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15
votes
1answer
958 views

Why did POKEing ROM addresses mask port writes?

After reading mcleod_ideafix's answer about the Inves Spectrum+'s "randomize of death", specifically his article on the subject, one thing struck me as odd. From César Hernández Bañó's research: ......
9
votes
1answer
2k views

Is this a bug or an allowed Pascal behavior?

Consider the following Pascal program: 1 1 PROGRAM MAIN(OUTPUT); VAR F:TEXT; I:INTEGER; 2 2 BEGIN 3 2 REWRITE(F); 4 3 FOR I := 10 TO 30 DO BEGIN 5 3 WRITELN( I, ’...
7
votes
2answers
1k views

Did general purpose I/O controller chips come with fewer than 40 pins?

I'm aware that 40-pins was a high-water mark for dual-inline package chips for a significant time; many CPUs of the early 1980s (8086, Z80, 6800, 6502, etc) used 40-pin packages, but no larger. ...
6
votes
2answers
328 views

Flash border color during Kernal LOAD routine

I would like to use the Kernal's LOAD routine to load a file into memory, because that seems to be the easiest way to do it. However, that LOAD call is synchronous in the sense that it returns once ...
5
votes
1answer
376 views

Why is my program outputting only zeros to the data bus during I/O operations?

I'm building a breadboard Z80-based computer. As now, I have the CPU hooked up to an EEPROM and an I/O device (an HD44780 character display) with appropriate decoding logic. The ROM chip starts at ...
4
votes
3answers
2k views

8086 duration of program

I have the following assembly code for 8086 MOV AL, [BX] OUT DX, AL The bus clock frequency is 1MHz. Access to memory is done without WAIT, and to I/O with one WAIT tick. How I can calculate the ...
4
votes
5answers
592 views

Are there any good resources on emulating/simulating early computing input/output?

Note: I hope this question is on topic. I'm not sure where else to put it. There are several tutorials available online for writing emulators/simulators. Unfortunately they all seem to focus on ...
2
votes
1answer
143 views

READY / WAIT when reading from / writing to IO ports

During the execution of an IN or OUT instruction (so after the opcode and its single-byte argument have been fetched from memory), how does the Intel 8080 react to its READY pin going down? Is it ...
1
vote
1answer
120 views

What kinds of input/output devices could the Electrologica X1 interface with (simultaneously)?

Here is a brief survey of the literature that I know of/have access to: The most complete description of the X1 that I am aware of is given in Dijkstra's 1959 PHD thesis, which describes in detail ...