Nuts & Volts - September 2005

Stamp

RX_DEC2:
 temp3 = 0
 FOR temp4 = 1 TO 2
 temp5 = RX_BYTE
 IF temp5 >= “0” THEN
 IF temp5 <= “9” THEN
 temp3 = temp3 * 10
 temp5 = temp5 - “0”
 temp3 = temp3 + temp5
 ELSE
 EXIT
 ENDIF
 ELSE
 EXIT
 ENDIF
 NEXT
 RETURN temp3

While it may not seem so at first, this code is identical to the RX_BIN8 subroutine. The difference, of course, is in the decimal base. To “shift” digits in this code, we need to multiply by 10, and then add the new value (after it’s converted from its ASCII code) to the result. Since we’re dealing in decimal and don’t want to overrun the limitations of a byte, the subroutine allows a maximum of two digits.

And now it gets a little hairy — but just a little.

Set_OnePort:
 TX_STR Pad
 idx = RX_DEC2
 TX_BYTE “ “
 cmd = RX_BYTE
 IF idx >= 1 THEN
 IF idx <= 8 THEN
 DEC idx
 temp1 = 1 << idx
 IF cmd = “1” THEN
 PortLo = PortLo | temp1
 ENDIF
 IF cmd = “0” THEN
 temp1 = ~temp1
 PortLo = PortLo & temp1
 ENDIF
 ENDIF
 ENDIF
 IF idx >= 9 THEN
 IF idx <= 16 THEN
 idx = idx - 9
 temp1 = 1 << idx
 IF cmd = “1” THEN
 PortHi = PortHi | temp1
 ENDIF
 IF cmd = “0” THEN
 temp1 = ~temp1
 PortHi = PortHi & temp1
 ENDIF
 ENDIF
 ENDIF
 TX_STR CRLF
 GOTO Main

This code is not as bad as it looks at first blush. What we have to remember is that SX/B is very close to assembly language (many instructions are 1-for-1), so it gets a bit verbose — certainly more than PBASIC.