Looks like you have plenty of room on that breadboard to prototype your entire Z80 project. Make sure you put plenty of 0.1uF bypass caps on the power rails. Sprinkle some around a bit.What do you think?
I am hoping so!Looks like you have plenty of room on that breadboard to prototype your entire Z80 project.
Correct.I am going to assume that the command "ADD A, n" means "add reg(a) and {this number}", correct?
In this example, you put the number "5" after the opcode for "ADD A, n". The CPU knows that the byte following the opcode for "ADD A, n" contains the value of n and not another opcode.If i am right, then how do if define the variable "n"? Since the opcode for "ADD A, n" is 11000110, let's say i want to add "A" with "5". How would i tell the cpu that n=11000110?
Address: Data: Comment:
0x0000 11000110 ADD A, (Opcode)
0x0001 00000101 n=5 (value)
0x0002 ???????? next opcode.That's normal. They blink in sympathy for the lower address line when those do the 7bit DRAM refresh addressing.Also, i noticed something else that really disturbs me. A7-A15 blink? Why is that?
Yes, any of the OUT or IN opcodes will cause the IORQ line to go active low.i figured that the variable would be stored in memory. Cool. Before i find out the hard way, i have yet another question. If the CPU needs to send data OUT of the data port, will IORQ go active?
Yes, that's all it does. You can use the HALT instruction to wait for an interrupt to occur.Also, what does the Halt pin do? Does it go active when the command "Halt" is executed?
Must have missed that post. If it has it's own display and keypad it'll be truly stand alone.I don't know if you read my post on the LCD i found, but i am thinking of using it as a monitor for it
You can use a 74xx245 which is a bidirectional tri-state buffer. It has a nicer pinout than the unidirectional 74xx244.Is there some type of chip that allows me to add tri-state to something? I think it would be called a Tri-State Buffer?
That is correct. I can scan a timing diagram for you if that helps.Ok, so if IORQ goes active, then MemRQ should go inactive, and then memory should be Z(High Impedance)?
You can use a 74xx245 which is a bidirectional tri-state buffer. It has a nicer pinout than the unidirectional 74xx244.
A logic IC reference
That is correct. I can scan a timing diagram for you if that helps.
The truth table shal set you free!When i say "i just hit another wall", i mean, i don't know ANY basic logic. Yes, i know, it is shameful, but i have a plan! I have a book on digital electronics, that explains digital logic.
I think you've studied the Z80 enough now that they should make sense.That would be great! But if you do that, then you will have to teach me how to read it. Every time i look at timing diagrams, i get very confused.
Think of it as looking at a multichannel scope hooked up the Z80 pins.None of that made any scence to me.
When they do that it is because those represent all 16 address lines and the 8 data buss lines. So d2, d4 & d7 could be high on the data buss and the rest low. So they draw it as a don't care or it could be anything scenario. So they draw the high AND the low at the same time and the X at the end. The X just represents the start of another state such as valid data when you transition from say invalid data.I have a question that bugs me, though. How can things be 0 and 1 at the same time? And then why does it make an "X" in some of the timmings?
Is it that blurry thing next to the other blurry thing?This is the MUX. If you look hard enough, you can see the transistor at the bottom right of the MUX. It is kinda under the arrow
There is nothing better than designing something yourself. Way more fun and you can use the parts you have on hand which leads to some pretty strange and creative things.The thing that makes me so proud, is that the digital selector circuit was ALL of my design. I didn't get schematics from anyone, nor did i ask for help. I just found the datasheet on the MUX, and connected it all, AND IT WORKED!
Is it that blurry thing next to the other blurry thing?
There is nothing better than designing something yourself. Way more fun and you can use the parts you have on hand which leads to some pretty strange and creative things.
Are you still trying to make your own assembler/compiler. Here is a command line operated one that works:
http://www.z80.info/zip/tasm301.zip
I have managed to build a programmer for loading code into a Z80 system in circuit via the parallel port. I'll post a schematic if you're interested. The software needs alot of work but at least it loads the binary data into RAM now. I don't have an EEprom to try it with, but I'm sure all that'll need doing is lengthening the time between data writes.
I'm having a little problem saving the schematic as a GIF right now. After all that drawing and now it won't save as an image.Yes, i would love to see your programmer. Is it just hardware? Or did you create software, too? Heck, i will take both! Thanks!
HL is a 16bit special register that is made from two 8bit ones (H & L). It's is commonly used to index memory or as a 16bit counter. IX and IY are also 16bit registers but they cannot be split into 2 8bit one like HL can.Oh, i almost forgot, is HL a register? On those OPCODES i got, HL is used often. (You know the ZIP file that had an XLS file in it...)
I'm having a little problem saving the schematic as a GIF right now. After all that drawing and now it won't save as an image.
I'll post both the software and the schematic once I get that figured out. One doesn't make sense without the other.
HL is a 16bit special register that is made from two 8bit ones (H & L). It's is commonly used to index memory or as a 16bit counter. IX and IY are also 16bit registers but they cannot be split into 2 8bit one like HL can.
I tried that. The problem, with Express Schematic, is when the whole schematic was on screen then there are no details for you even to guess what it is. I could have zoomed, scrolled around and done 4 print screen's and pasted it together but what a pain. I managed to fool it by changing the paper size but then it put the boarder in the middle of the diagram which I had to photo shop out. Grrr!Well, if you don't want to go through all of that work, then you can just push [CNTRL]+[PRT SCR], then [ALT]+[PRT SCR], and that will take a screen shot of any window you have up. Then just paste it into an image editor.
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