24 bit math so I can read and write

You hit on it below. You read/write 3 8 bit pieces.

Well it kinda' depends. How is the variables laid our in memory? If it were an HC05 part I would know the variable is most likely stored as three 8 bit values with the lowest address holding the upper byte address+1 is the middle byte and address+2 is the low byte. Other CPU/MCUs do it just the opposite. Google "big endian" or "little endian" Now, all you have to do is send those 3 bytes and you are done. If you are using a high level language that supports INT24s then the task is even easier. Just do shifts and mask off the byte you want to send.

Jim

Jim, I am using a Basic Stamp BS2.

If the platform you are using does not support numbers large enough for your needs, then you need to roll your own routines. A while back, I worked on an application that performed 24 bit arithmetic with an 8 bit Motorola 65xx series processor. The math routines were modeled after the grade school methods of long hand multiplication and division.

As far as transferring or storing data, it doesn't matter what format it is in. To the computer it is all the same. You need to decide on the protocol that will be used between the devices. The data doesn't matter, the key is how it is interpreted.

OK, what are you sending this 24bit data to and how is it being sent (uart, I2C, so on).

Jim

You might want to check on the PICAXE forum

There's been recent discussion on how to do 24 (and 32) bit arithmetic. Since the PICAXE is programmed in a dialect of BASIC, the conversion to Stamp should be relatively simple.

John

I might have been a bit slow, BUT I think he is trying to write to some type of device's configuration register. If that is the case just hard coding the three bytes into the code would be good enough to get by. I think what threw me was the "math" word.

Jim