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

You're right, which is why I don't use the LOOKDOWN approach in my programs that accept serial commands.  While it may seem verbose, checking the characters as they come in prevents issues.  For example, our FC-4 fader board uses this bit of code for processing commands from the master:

[code]Main:
  char = RX_BYTE                                ' wait for header
  IF char <> "!" THEN Main
  char = RX_BYTE ToUpper
  IF char <> "F" THEN Main
  char = RX_BYTE ToUpper
  IF char <> "C" THEN Main
  char = RX_BYTE
  IF char <> "4" THEN Main


Check_Addr:
  char = RX_BYTE                                ' rx addr
  allCall = No                                  ' clear global request
  IF char = CmdAll THEN                         ' all call requested?
    allCall = Yes                               '   yes, set flag
    GOTO Get_Cmd                                '   and skip ID check    
  ENDIF
  addr = %00                                    ' clear old setting
  addr.0 = ~A0                                  ' get low bit of address
  addr.1 = ~A1                                  ' get high bit of address
  IF char <> addr THEN Main                     ' validate


Get_Cmd:
  char = RX_BYTE ToUpper                        ' rx command byte
  IF char = "V" THEN Show_Version
  IF char = "G" THEN Get_Status
  IF char = "L" THEN Set_Level
  IF char = "S" THEN Set_All
  IF char = "P" THEN Preset_All
  IF char = "A" THEN All_On
  IF char = "D" THEN Digital_Control
  IF char = "X" THEN Reset_All 
  IF char = "F" THEN Fader
  IF char = "C" THEN Cross_Fade
  GOTO Main[/code]
It may seem verbose, but as the style is close to the assembly output it doesn't take a lot of code, and it's quite easy to add or disable features while testing.

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