'***************************************************************************
'*                                                                         *
'*                              SAMPLE 1                                   *
'*                       LOOP BACK TEST PROGRAM                            *
'*                                                                         *
'* This program uses the loop back feature of the 16450 chip to transmit   *
'* a sequence of characters and in turn receive them.  No external jumpers *
'* are required to run this program.                                       *
'*                                                                         *
'* LAST MODIFIED: 2/5/98                                                   *
'***************************************************************************

DECLARE FUNCTION AskForBaseAddress! (OldOne AS INTEGER)


  RECEIVE = 0           ' Receiver buffer register
  TRANSMIT = 0          ' Transmitter holding register
  LDIVISOR = 0          ' Divisor latch, least significant byte
  UDIVISOR = 1          ' Divisor latch, most significant byte
  INTENB = 1            ' Interrupt enable register
  INTID = 2             ' Interupt identification register
  LINECTRL = 3          ' Line control register
  MODEMCTRL = 4
' Modem control register
  LINESTAT = 5          ' Line status register
  MODEMSTAT = 6         ' Modem status register



ch% = 0
ch1% = 0

CLS

PRINT "                 Sample1.BAS   :  Internal Loopback Test"
PRINT
PRINT "This program uses the loop back feature of the 16450 chip to transmit "
PRINT "a sequence of characters and in turn receive them.  No external jumpers"
PRINT "are required to run this program."
PRINT
PRINT
Address% = AskForBaseAddress!(&H350)


CLS
PRINT : PRINT : PRINT
PRINT "Board Configuration:"
PRINT
PRINT " -- Base Address is "; HEX$(Address%); " hex"
PRINT " -- All remaining jumper settings are irrelevant."
PRINT : PRINT : PRINT
INPUT "Press Enter to Continue  "; Msg$


' First, set up the divisor latches for 9600 baud.  A divisor of 12 is
' required since the 1.8432 clock is used.  The upper divisor is set to
' 0 and the lower to 12.
OUT Address% + LINECTRL, &H80
OUT Address% + LDIVISOR, &HC
OUT Address% + UDIVISOR, &H0
' Now set the line control register for the following communications
' protocol:
'                bit0, bit1 = 1 -- character is eight bits
'                      bit2 = 0 -- one stop bit
'                      bit3 = 0 -- no parity is enabled
'                      bit4 = 0 - -doesn't matter with parity disabled
'                      bit5 = 0 - -doesn't matter with parity disabled
'                      bit6 = 0 -- disable break control
'                      bit7 = 0 -- DLAB bit, 0 disables divisor latches
OUT Address% + LINECTRL, &H3

' Enable the loop back feature of the chip with bit 4 of modem control
' register, now all transmitted characters will be looped back to the
' receiver, without external connections.
OUT Address% + MODEMCTRL, &H10

' These inputs are just to insure that both the receiver buffer register
' and receiver shift register are clear.

FOR x% = 1 TO 4                  ' Acts as a delay between OUT's
NEXT x%
ch% = INP(Address% + RECEIVE)    ' clear rx registers
FOR x% = 1 TO 4                  ' Acts as a delay between OUT's
NEXT x%
ch% = INP(Address% + RECEIVE)

'***********************************************************
'*                                                         *
'*     Transmit the letters 'A' through 'Z', and in turn,  *
'*  receive the characters, and check if the correct char  *
'*  is received.  The program will print an error message  *
'*  for each bad character received. If no errors occur,   *
'*  the program will indicate so at the end of program     *
'*  execution.                                             *
'*                                                         *
'***********************************************************

flag = 0
FOR ch% = 65 TO 90                       ' ASCII codes for A to Z
    OUT Address% + TRANSMIT, ch%         ' send character to UART
    DO
      ch1% = INP(Address% + LINESTAT)    ' poll line control register
    LOOP UNTIL (ch1% AND 1) > 0
    ch1% = INP(Address% + RECEIVE)       ' read the input char

    ' check if char received is the one we sent
    IF ch1% <> ch% THEN
      PRINT "error with character "; CHR$(ch%); ", received char "; CHR$(ch1%); "."
      flag = 1
    END IF
NEXT
IF (flag = 0) THEN ' then no errors occured
  CLS
  PRINT : PRINT : PRINT : PRINT : PRINT
  PRINT "All characters were transmitted without error."
END IF
END

FUNCTION AskForBaseAddress (OldOne AS INTEGER)
   Msg$ = ""
   NewOne% = 0: Success = 0: Dummy% = 0
   AddrInputPosX = 0: AddrInputPosY = 0

   PRINT "Please enter the Base Address (0000-FFFF) for your card (in hex)"
   PRINT "or press ENTER for "; HEX$(OldOne%); "."
   PRINT ">";
   AddrInputPosX = POS(0): AddrInputPosY = CSRLIN
   WHILE Success = 0
     LOCATE AddrInputPosY, AddrInputPosX
     PRINT "                                                                               "
     LOCATE AddrInputPosY, AddrInputPosX
     LINE INPUT Msg$
     NewOne% = VAL("&H0" + LEFT$(Msg$, 4))
     Success = 1
     Dummy% = NewOne%
     IF (Msg$ = "") THEN
        LOCATE AddrInputPosY, AddrInputPosX
        PRINT HEX$(OldOne%)
        Success = 1
        Dummy% = OldOne%
     END IF
  WEND
  AskForBaseAddress = Dummy%
END FUNCTION