Help on this one appreciated.

If i have a ROM chip with 14 address lines how can i determine its capacity in ROM.?
I think it equates to 16384 (16K), not sure though. A more detailed explanation from someone who has the KNOWLEDGE would help me on my way.
Help received so far been brilliant by the way!!!!!!!!
thanx in advance
Neil

2^14=16K. This ROM would usually be 16Kx8, or 16,384 bytes.

It'll be 16K somethings, but the somethings aren't necessarily bytes. The way to find out is to count the data bits. If there's 8, it's 16KB. Some ROMs have 16 - in that case it'd be 32KB (16K * 2 bytes).

That's why memory devices are usually sold as having a certain number of bits: a 1Mb DRAM will contain 1048576 bits. They could be organised as 1048576 words of 1 bit each, or 262144 words of 4 bits, or...

Neil,

How do you know it has 14 address lines, unless you have some info on it (mainly meaning a data sheet)? If it's programmable (PROM, EPROM, EEPROM, or something like that), it should have a number printed on it that you can look up. If it's mask-programmed, it probably has a proprietary number on it that won't mean anything outside the company that made it (or got it made for them). "Mask-programmed" means the final data content is determined by the masks used in the wafer fabrication, instead of by programming after manufacture. If it's some kind of programmable ROM, you can probably find a data sheet on it. (I should add that although we call them data "sheets", they are usually far more than just one sheet or page.) A very common 16KB EPROM has been the 27C128. "27" is the EPROM family, "C" means "CMOS", and the "128" means 128 kilobits. Most ROMs are byte-wide (meaning they have 8 data pins), unlike DRAMs, which are often 1, 4, 8, or 9 bits wide, and are built into modules up to 36 bits wide.

Garth