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

Gordon,

Don't be disuaded by that term "non optimizing."  Parallax happens to be very honest in its approach, most companies would never mention that about the same kind of compiler.  But let me show you that this is NOT a problem, and gets you into the SX very quickly.  And help you learn assembly as you can see the compiled output (you can even modify it to experiment).

I'm part of the EFX group and we have some new serial modules coming that use the SX and are completely programmed in SX/B.  Yes, we use our own tools to develop products.  The devices we're creating follow the Parallax AppMod protocol, and generally want to wait on a specific header, for example, something like this:

   "!EFX"

If we code for that header like this:

Main:
  SERIN Sio, Baud, char
  IF char <> "!" THEN Main
  SERIN Sio, Baud, char
  IF char <> "E" THEN Main
  SERIN Sio, Baud, char
  IF char <> "F" THEN Main
  SERIN Sio, Baud, char
  IF char <> "X" THEN Main

... it works, but each instance of SERIN uses of a bit of code space.  So we can hand-optimize (which assembly programmers do all the time) by putting SERIN into a subroutine:

RXBYTE:
  SERIN Sio, Baud, temp1
  RETURN temp1

Now the SERIN code is compiled in just one place.  As of version 1.3, subroutines can behave like functions, so the header block above would be recoded as:

Main:
  char = RXBYTE
  IF char <> "!" THEN Main
  char = RXBYTE
  IF char <> "E" THEN Main
  char = RXBYTE
  IF char <> "F" THEN Main
  char = RXBYTE
  IF char <> "X" THEN Main

Since -- other than the PBASIC-like commands -- SX/B is a light version of BASIC, most lines of code translate 1-to-1 to assembly.  SX/B is free ... so it does't hurt to give it a try and mix in assembly as you get more comfortable with it.

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