Hello Paul
On Tuesday, 17 March 1998 13:07:00, you wrote to All:
 PR> in an example in qbasic, i saw this &H3FC which stands for com
 PR> 1 but i cant find the address for ports 1-4 it was used in the
 PR> example.... INP(&H3FC) with OUT etc if anyone can help me about the
 PR> above address please let me know... cya
The following ports are assigned to the four serial ports:
02E8-02EF : COM4
02F8-02FF : COM2
03E8-03EF : COM3
03F8-03FF : COM1
Here are their function (for COM1, analog for others):
03F8  -W  serial port, transmitter holding register (THR), which contains the
          character to be sent. Bit 0 is sent first.
          bit 7-0  data bits when DLAB=0 (Divisor Latch Access Bit)
03F8  R-  receiver buffer register (RBR), which contains the received
          character. Bit 0 is received first
          bit 7-0  data bits when DLAB=0 (Divisor Latch Access Bit)
03F8  RW  divisor latch low byte (DLL) when DLAB=1 (see #P201)
03F9  RW  divisor latch high byte (DLM) when DLAB=1 (see #P201)
03F9  RW  interrupt enable register (IER) when DLAB=0 (see #P202)
03FA  R-  interrupt identification register (see #P203)
          Information about a pending interrupt is stored here. When the ID
          register is addressed, thehighest priority interrupt is held, and
          no other interrupts are acknowledged until the CPU services that
          interrupt.
03FA  -W  16650 FIFO Control Register (FCR) (see #P204)
03FB  RW  line control register (LCR) (see #P205)
03FC  RW  modem control register (see #P206)
03FD  R-  line status register (LSR) (see #P207)
03FE  R-  modem status register (MSR) (see #P208)
03FF  RW  scratch register (SCR)
          (not used for serial I/O; available to any application using 16450,
          16550) (not present on original 8250)
(R = read, W = write)
Copied from Ralf Brown's Interrupt List.
Friendly greeting you,
Hans Lunsing,           Fido     : 2:500/104.6955
                        Internet : jlunsing@doge.nl
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