'===========================================================================
' Subject: COM ROUTINES                      Date: 11-09-95 (02:12)       
' Author:  Chad Beck                         Code: QB, QBasic, PDS        
' Origin:  FidoNet QUIK_BAS Echo           Packet: MODEM.ABC
'===========================================================================
' > I am STILL in need of a routine to initialize com ports 1 through 4
' > at speeds  up to hopefully 115,200bps... My routines have stopped
' > working. I do NOT need  any routines for writing/reading port data,
' > all I need is something to set the  bps rate, and maybe the parity,
' > data bits, and stop bits as well. Doesn't anyone have source that
' > meets these requirements?

'     Alright, alright.  You've suffered long enough.  To set the BPS
'rate, first you need to calculate the Baud Rate Divisor, then set bit 7
'of the Line Control Register on, then write the Baud Rate Divisor, the
'set bit 7 of the Line Control Register back off.  This is untested:

    BRD = 1843200 \ (16 * BitRate)           'calculate Baud Rate Divisor

    Byte = INP(ComAddress + 3) OR 128        'set bit 7 of LCR high
    OUT ComAddress + 3, Byte

    OUT ComAddress + 1, BRD \ 256             'MSB of BRD
    OUT ComAddress, BRD AND 255               'LSB of BRD

    Byte = INP(ComAddress + 3) AND 127       'set bit 7 of LCR low
    OUT ComAddress + 3, Byte

                                ---***---

     The Parity, Data & Stop bits are easier:

    OUT ComAddress + 3, Byte

     The bit values of Byte are as follows (I'll spare the high ASCII):
------------------------------------------------------------------------
|   Bit #      Meaning             Setting                             |
|----------------------------------------------------------------------|
|    0-1       Character length                                        |
|                   5 bits           00                                |
|                   6 bits           01                                |
|                   7 bits           10                                |
|                   8 bits           11                                |
|     2        Stop bits                                               |
|                   1 bit             0                                |
|                   1.5 bits          1 (5-bit characters)             |
|                   2 bits            1 (6, 7 & 8-bit characters)      |
|    3-5       Parity                                                  |
|                   Ignore           000                               |
|                   Odd              100                               |
|                   Even             110                               |
|                   Mark             101                               |
|                   Space            111                               |
|     6        Break condition                                         |
|                   Disabled          0                                |
|                   Enabled           1                                |
|     7        Port toggle                                             |
|                   Normal            0 (use THR/RDR & IER registers)  |
|                   Alternate         1 (use BRDL & BRDH registers)    |
|                                                                      |
------------------------------------------------------------------------

     So, for instance, 8 data bits, 1 stop bit and no parity is 00000011
binary (3) while 7 data bits, 1 stop bit and even parity is 00011010
binary (26).
     Make sense?  Let's hope so.