is a register in an AVR always 8 bits?

A register is sram, and they are all 8 bits, however the specials registers and some IO ports extend over multiple registers or IO ports.

EX: The X, Y, or Z memory pointers. Those 16-bit values exist over two registers.

So often you end up with code like: ldi XL, LOW(blahblahaddr) ldi XH, HIGH(blahblahaddr)

an

A macro does this for you. I use this macro to do

SetXPtr blahblahaddr

Rene

Brett wrote:

"Brett" wrote in news:bgl3vu$oph5v$ snipped-for-privacy@ID-184277.news.uni-berlin.de:

Oh - so you're saying tha the LOW() macro returns the first byte of a 2 byte register and the HIGH() macro returns the second byte of a 2 byte macro? I had seen those in use and had been really really confused by them!

No, the registers are *always* 8 bits.

The instructions above are "load immediate" which means to load a constant value into a register. The LOW and HIGH macros return the low and hogh bytes respectively of the constant.

Thus, the XL register which is 8 bits, is loaded with the low 8 bits of the constant "blahblahaddr". Likewise for the XH register.

Good day!