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How to Start hardware of 8085up......??

Don't forget that the 8085 also mirrors the 8-bit I/O address in the upper address byte. That makes expansion really easy, as you do not need to demultiplex the address and data buses to obtain an I/O address. The simplest latched input or output port could be constructed with a 74LS373 latch, a 74LS688 comparator, one inverter/NOT gate, and an 8-position DIP switch. Qualify the 74LS688 by inverting the IO//M line and feeding it into the 74LS688's /E pin, and tie the /LE pin of the 74LS373 to the /RD or /WR line, depending on if you want an input or output port. For the board real estate, you might be better off with a 8255 PIA (or the 8085 bus-specific 8155).
 
I figure he's going to want to put some memory on this thing (anticipating his next question, I guess), so he might as well demux the lower 8 bits--he's going to need them. The 8085-specific stuff such as the 8755 are pretty hard to come by.
 
Writing to a port is simple in theory; you just execute the OUT b instruction, where b is your 8 bit IO address , the data sent comes from the A register. This is done in much the same way as writing to memory except IO/M is high not low. On the hardware side you'll want a latch most likely, if you just want to blink an LED a single D-type Flip Flop like the 74LS074 will do with the LED and a resistor on the Q and D to D0. The CLK could then be connected to an AND gate's output with IO/M and NOT ALE as inputs <--- you'll need both an AND gate and a NOT gate. As you should see, this means the first bit from the data bus will be stored when the processor has outputted any IO address (this is ignored, ALE is low to show the data (from the accumulator) is now on the AD bus). Interfacing the eeprom is more of a challenge, you will need to latch the address and make sure it does not respond to IO ports (IO/M to /CE?) you will need an octal latch (74LS373) to latch the address (Enable to ALE, AD0-AD7). I recommend you do it in stages; first do a pull down no-op run, then do an eeprom run and then a IO port run, an oscilloscope is valuable when checking the results.

I HIGHLY recommend (if nothing else) you read from these sites:
8080 Instruction Set
The 8085 Project Page
The 8085 Trainer Project

Keep in mind, the more things you want (RAM etc) the more complex it'll get (support logic wise).
 
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I assume you mean using the parallel port as an eeprom? Or programming the eeprom with a parrallel port? Either way you'll need support logic, the 8085 is a microprocessor, very different to a microcontroller as there are no onboard devices other than the ALU, clock generator, registers and control logic. If you're not wanting to spend much you could build your own eeprom programmer or buy a willem programmer. If you just want to test your programs use GNUSim 8085/.
 
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So, there is no chance of getting any info. about parallel port or printer port for taking some logic outputs
 
RITESH said:
So, there is no chance of getting any info. about parallel port or printer port for taking some logic outputs
Click to expand...

There is plenty of information on using the PC parallel port for controlling devices. A quick Google search should yield lots of results. How you access the parallel port will depend on the operating system you are using. For development under Linux, I like the parapin C library.
 
How you access the parallel port will depend on the operating system you are using. For development under Linux, I like the parapin C library.
Click to expand...

I have widow XP intel i3 processor......is this enought to have idea..??
 
It may be, but not from me -- I don't develop for Windows. I believe there's a version of the parapin library for C++ under Windows, but I've never used it. I do know that hardware port access is radically different in Windows NT-based systems than DOS-based systems.

You probably want to start a new thread for this discussion, as it has nothing to do with 8085s and isn't really vintage computer related.
 
glitch said:
It may be, but not from me -- I don't develop for Windows. I believe there's a version of the parapin library for C++ under Windows, but I've never used it. I do know that hardware port access is radically different in Windows NT-based systems than DOS-based systems.
Click to expand...

Those of us who use parallel-port JTAG and ISP interfaces know that a special driver; usually GIVEIO that allows a Win32 program to directly access the parallel port.
 
Hi again,

Please tell what to write in EEPROM i have got 2864 and 74193 for add. by micro switch 4bit counters in both up/down. I will cascade the counters .......
The program to will be written by switches. and what about the programming pin in 2864 EEPROM??
please tell the procedure now..!!

Thanks
 
The 74193 is working fine but the problem is some time when switch is pressed once the the counter jump from 1 to 3 like ths.....

I think this the problem of denounce..!!


please help.
 
You can make a simple debounce cirquit out of a pair of resistors, a capacitor, a diode and a schmidt-triggered buffer.

Code: 
+5V -----+
         |
         |
         <
         >
         <
         |                |`\
         |                |  `\
         +----|>|----+----| [] >----- Out
         |           |    |  /´
         +--/\/\/\---+    |/´
         |           |
         |           |
         +          ---
        \           ---
         +           |
         |           |
GND -----+-----------+
 
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OK, today i have implemented the denounce circuit using NAND gate....
it is working well and i have also cascade the 1983 chip but when taking out the carry to the input of counter of 2nd 193 chip it has 1 on its output .....
so when it start add. the 2nd chip shows 1 which should be 0.

I think i need, NOT gate to reverse the direction voltage level or with transistor..
the 2864 chip i am using is here:-

http://www.alldatasheet.com/datasheet-pdf/pdf/105285/CATALYST/CAT28C64A.html

as old EEPROM use 25Volt for programming but how much this will take
Please send the circuit to make EEPROM programmer..!!


Thanks
 
If you plan on putting 25V as Vpp on a 2864, plan also on spending a lot of money buying replacement EEPROMs. :shock: The 2764 UV EPROM uses 25V as Vpp (in some versions).

The data programming instructions are very clear in the datasheet you pointed to. If you are uncomfortable, I would recommend that you purchase a pre-built programmer. Willem is one popular type--it is offered by many vendors.
 
I am using 5V supply for counter connecting this 5V at write pin of 2864 will work...??
please cl;ear my doubt and is there any time limit for triggering the write pin??
 
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