can a AT89C51 be used as a rom?

[777xxx]

so i can connect it to an external cpu and run code off it? ive looked on google and cant find any definitive answers. i know it uses flash ram but if i only want to read from it, would this be a problem? and if so, where would i connect the address and data lines? any help would be appreciated.

 

[Papabravo]

You can't tell it what address you want to get data from so there would be no way to get data from the particular address you want.

 

[Nigel Goodwin]

Assuming you've got enough I/O lines available, you could program a micro-controller to work as a crude and very slow ROM, but it seems a pretty pointless thing to do.

 

[777xxx]

Assuming you've got enough I/O lines available, you could program a micro-controller to work as a crude and very slow ROM, but it seems a pretty pointless thing to do.

ive got 32 io lines available. does such a program exist? or could someone write it?

 

[Nigel Goodwin]

ive got 32 io lines available. does such a program exist? or could someone write it?

I've no idea if such a programme exists or not, as it's such an unusual idea, perhaps not? - exactly why do you want to do this?, and exactly what do you want to do?. Why not just copy the code to the other device?.

 

[777xxx]

I've no idea if such a programme exists or not, as it's such an unusual idea, perhaps not? - exactly why do you want to do this?, and exactly what do you want to do?. Why not just copy the code to the other device?.

its the only chips and programmer i have available at the moment

 

[Ian Rogers]

Personally I don't think it would work. The 8051 device controls the address bus, so an external device would have to be in serial control, bit banging an address bus externally, then decoding it and reading the code and sticking it on the data bus would take longer than a serial connection, so as Nigel already said it would be piggin slow. 8051;s do have the ability to read external rom, but from a rom chip..

 

[Nigel Goodwin]

its the only chips and programmer i have available at the moment

It's FAR too much work for such a reason, and would perform appalling slowly - just buy some better chips - or just use a simulator on your computer, which would run a lot faster.

 

[777xxx]

It's FAR too much work for such a reason, and would perform appalling slowly - just buy some better chips - or just use a simulator on your computer, which would run a lot faster.

my programmer is a sp200s-v2.00, so what chips should i get?

 

[Nigel Goodwin]

Personally I don't think it would work. The 8051 device controls the address bus, so an external device would have to be in serial control, bit banging an address bus externally, then decoding it and reading the code and sticking it on the data bus would take longer than a serial connection, so as Nigel already said it would be piggin slow. 8051;s do have the ability to read external rom, but from a rom chip..

I don't see why not (although it depends on your definition of 'work')

It should be possible to write a program to emulate a ROM, 16 I/O lines for address input, 8 I/O lines for data output, plus the usual handful of handshaking lines - but as we've said all along, it will be horribly slow.

But as the OP seems to live in the civilised world he could get some decent devices for little coat next day.

 

[Nigel Goodwin]

my programmer is a sp200s-v2.00, so what chips should i get?

I've no idea, I've never used (or heard of) it.

I've always used PIC's, which is one of the most popular devices from a single manufacturer, a lot really depends on what you're wanting to do.

 

[777xxx]

I've no idea, I've never used (or heard of) it.

I've always used PIC's, which is one of the most popular devices from a single manufacturer, a lot really depends on what you're wanting to do.

use them as roms

 

[Nigel Goodwin]

use them as roms

Why? - if you want a ROM, then use a ROM - or an EPROM (more likely) or an EEPROM.

 

[777xxx]

Why? - if you want a ROM, then use a ROM - or an EPROM (more likely) or an EEPROM.

i dont have the programmer for it

 

[Ian Rogers]

That programmer doesn't support much.. Invest in a TL866II I paid about £50 and it support tons of devices.

I even program small GAL's as well.