In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:

Rodney,

in Assembly, I use some naming conventions that help to keep the banks in order. Here is an example of how I declare banks and registers:

org                   $10
Ser                   = $
Ser_TxHighPC     ds  1
Ser_TxLowPC      ds  1
Ser_TxCountPC   ds  1
Ser_TxDividePC   ds  1
Ser_RxBytePC     ds  1
Ser_RxCountPC   ds  1
Ser_RxDividePC   ds  1

As you can see, I assign a name to each bank, like "Ser" in this example. I then prefix the names of all registers in this bank with the bank name, followed by an underscore.

In the code, something like

bank  Timer
mov   Ser_TxHighPC, #'?'

should look really suspicious, as a register in bank "Ser" is referred to after bank "Timer" has been selected.

It is getting more problematic when you need to copy from a register in one bank to a register in another bank. In simple cases, you may use the W register as temporary storage, as in

bank Timer
mov w, Timer_Count
bank Serial
mov Serial_TxLow, w

Always be aware that the W register is used as temporary storage by almost all comopund statements, so this code will fail:

bank Timer
mov w, Timer_Count
mov Timer_Count, #200          ; w is used as temporary storage !
bank Serial
mov Serial_TxLow, w

When you replace the compound statement by what the assembler generates, you will immediately notice the problem:

bank Timer
mov w, Timer_Count
;-------------------------
; mov Timer_Count, #200
;
mov w, #200              ; This overwrites the value of Timer_Count in w
mov Timer_Count, w
;-------------------------
bank Serial
mov Serial_TxLow, w   ; 200 is written to Serial_TxLow but not Timer_Count

For such cases, it is a good idea to have a temporary register defined in the global area, as such registers can always be accessed, no matter which bank is selcted. Here is an example:

bank Timer
mov Temp, Timer_Count
mov w, #200
mov Timer_Count, w
bank Serial
mov Serial_TxLow, Temp

Enough for now.... :-)

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=421700#m423371

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2010 (http://www.dotNetBB.com)