BS2 Nibbles for SX/B ?? How can it be done.

T&E Engineer · 2007-03-24 03:05

I have a BS2 program I am trying to convert over to SX/B. However, it uses nibbles. I thought there was a _LSB and _MSB command variable that can be used but I think that may only work on WORDs (down to bytes - not nibbles).

'BS2 code
secs············ VAR···· Byte··················· ' seconds
secs01········· VAR···· secs.LOWNIB
secs10········· VAR···· secs.HIGHNIB

I tried in SX/B the following - errors (as expected):

secs············ VAR···· Byte··················· ' seconds
secs01········· VAR···· secs_LSB
secs10········· VAR···· secs_MSB

What is the equivalent in SX/B?

T'Saavik · 2007-03-24 06:27

I'm a total noob here, but maybe try this out to get at the bits tell the pro's wake up and tell you the better way:

secs0001 = secs.0
secs0010 = secs.1
secs0100 = secs.2
secs1000 = secs.3

Checkout the "SX/B Defintions" chapter in the SX/B online help.

Bean · 2007-03-24 12:02

SX/B doesn't have a nibble variable type. Neither does the propeller.
The nibble is not a standard variable type, I believe it was used on the BS2 to save RAM.

You'll have to seperate the values in the code:

GetSecs
Secs01 = Secs AND $0F
Secs10 = Secs >> 4

Bean.

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T&E Engineer · 2007-03-24 12:10

Thanks.

Is GetSecs a label or something (e.g. GetSecs: )?

Should it be like this?

Secs············ VAR···· Byte··················· ' Seconds

Secs01········· VAR···· Secs

Secs10··········VAR·····Secs

GetSecs:
Secs01 = Secs AND $0F······················ ' Secs01 = %xxxx1111
Secs10 = Secs >> 4··························· ' Secs10 = %1111xxxx

Post Edited (T&E Engineer) : 3/24/2007 12:34:23 PM GMT

JonnyMac · 2007-03-24 15:44

If you declare secs01 and secs10 as aliases of secs then the second line:

secs10 = secs >> 4

will always return 0 (because the preceding line stripped off the upper nibble). Unfortunately, the ease-of-use of the BASIC Stamp and its great language features have made many of us lazy and that shows up when we switch to a core processor like the SX. The great thing about SX/B, however, is that it's easy to extend the language via subroutines and functions. I do this:

DEC2BCD         FUNC    1, 1
BCD2DEC         FUNC    1, 1

... and then code those functions like this (both accept and return one byte):

DEC2BCD:
  tmpB1 = __PARAM1                              ' get parameter
  tmpB2 = tmpB1 / 10                            ' isolate 10s
  SWAP tmpB2                                    ' move to upper nibble
  tmpB2 = tmpB2 | __REMAINDER                   ' add lower nibble
  RETURN tmpB2

BCD2DEC:
  tmpB1 = __PARAM1                              ' get parameter
  tmpB2 = tmpB1 >> 4                            ' isolate high nibble
  tmpB2 = tmpB2 * 10                            ' convert to decimal
  tmpB1 = tmpB1 & $0F                           ' isolate ones
  tmpB2 = tmpB2 + tmpB1                         ' add them
  RETURN tmpB2

Note on DEC2BCD: You have to be careful about using __REMAINDER; this code works because the SWAP instruction does not modify __PARAM1 (an alias of __REMAINDER) -- you will usually use __REMAINDER immediately after the division. I've tested these routines with values 0..99 and $0..$99 -- they work.

Post Edited (JonnyMac) : 3/24/2007 3:57:19 PM GMT

BS2 Nibbles for SX/B ?? How can it be done.

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