Tech Arsenal 1/Tech Arsenal (Arsenal Computer).ISO/tek-05/pcb121.zip/I8250.INC

Text File | 1992-01-23 | 17KB | 443 lines

;;*****************************************************************************
;;                         i8250.inc      i8250.inc
;;*****************************************************************************
;;
;;  Copyright (C) 1990 Vance Morrison
;;
;;
;; Permission to view, compile, and modify for LOCAL (intra-organization)
;; USE ONLY is hereby granted, provided that this copyright and permission
;; notice appear on all copies.  Any other use by permission only.
;;
;; Vance Morrison makes no representations about the suitability
;; of this software for any purpose.  It is provided "as is" without expressed
;; or implied warranty.  See the copywrite notice file for complete details.
;;
;;*****************************************************************************
;; this software essentially is responsible for setup of the 8250 and
;; getting individual chacters off the serial line.   The routines here
;; where designed so that they will work with the 16550AF and take advantage
;; of that chip's read and write FIFOs.
;;
;; The functions provided by this file are
;;
;;   I8250_DECLARE name, port_prefix, port, io_addr, irq, flow
;;   I8250_DEFINE_in_BX name, fail
;;   I8250_WRITE_in_AL_const_BX_BP_ES MACRO name
;;   I8250_CAN_WRITE_const_BX_CX_BP_SI_DI_ES MACRO name not_ready
;;
;;      the following 'upcall' routines will be called from interupt level
;;  <port_prefix>_CONSUME_in_AL_const_BX_BP_ES 'port'
;;  <port_prefix>_WRITE_EMPTY_const_BX_BP_ES 'port'
;;
;;   i8250_&name&_declared                  ;; one if this interface exists
;;   i8250_declared                         ;; one if ANY interface exists
;;
;;******************************************************************************


;; 'standard' port numbers
IBM_COM1_PORT = 3F8H
IBM_COM2_PORT = 2F8H
IBM_COM3_PORT = 3E8H
IBM_COM4_PORT = 2E8H

;; and interupts
IBM_COM1_IRQ = 4
IBM_COM2_IRQ = 3

;; the 10 registers of the 8250
I8250_REG_THR = 0       ;; trans hold reg (LCR_DIVISOR = 0) (write only)
I8250_REG_RDR = 0       ;; rec data reg (LCR_DIVISOR = 0) (read only)
I8250_REG_DIVL = 0      ;; baud rate divisor (LCR_DIVISOR = 1)
I8250_REG_DIVH = 1      ;; baud rate divisor (LCR_DIVISOR = 1)
I8250_REG_IER = 1       ;; interupt enable  (LCR_DIVISOR = 0)
I8250_REG_IIR = 2       ;; interupt ident (read only)
NS16550_REG_FIFO = 2    ;; FIFO control register for the NS16550AF chip
I8250_REG_LCR = 3       ;; line control
I8250_REG_MCR = 4       ;; modem control
I8250_REG_LSR = 5       ;; line status
I8250_REG_MSR = 6       ;; modem status
NS16550_REG_SCR = 7     ;; Scratch register.

;; masks for the IER
I8250_IER_DIN   = 1H        ;; interupt on data in
I8250_IER_DOUT  = 2H        ;; interupt on data ready for out
I8250_IER_ERR   = 4H        ;; interupt on data error
I8250_IER_MODEM = 8H        ;; interupt on modem status change

;; masks for the IIR
I8250_IIR_NOINT   = 1H      ;; the rest of IIR valid only if this bit is 0
I8250_IIR_TYPE    = 6H      ;; type of highest priority interupt
NS16550_IIR_CHECK = 0C0H    ;; Both of these bits must be 1 if its a 16550AF

;; values for type field of the IIR (read only)
I8250_TYPE_MODEM  = 0H      ;; notice they are shifted to the TYPE field
I8250_TYPE_DOUT   = 2H
I8250_TYPE_DIN    = 4H
I8250_TYPE_ERR    = 6H

;; masks for the FIFO reg   (write only)
NS16550_FIFO_ON   = 1       ;; Enable the FIFOs
NS16550_FIFO_FIN  = 2       ;; Flush input FIFO
NS16550_FIFO_FOUT = 4       ;; Flush input FIFO
NS16550_FIFO_TRIG = 0C0H    ;; bytes in input FIFO before interupt

;; values for the TRIG field of the FIFO reg
NS16550_TRIG_1    = 000H    ;; trigger on 1 byte
NS16550_TRIG_4    = 040H    ;; trigger on 4 bytes
NS16550_TRIG_8    = 080H    ;; trigger on 8 bytes
NS16550_TRIG_14   = 0C0H    ;; trigger on 14 bytes

;; masks for the LCR
I8250_LCR_BITS    = 3H      ;; number of bits - 5
I8250_LCR_STOP    = 4H
I8250_LCR_PARITY  = 38H
I8250_LCR_BREAK   = 40H     ;; send a break
I8250_LCR_DIVISOR = 80H     ;; make reg 0,1 be the divisor register

;; values for the parity field of the LCR
I8250_PARITY_IGN   = 0H     ;; notice they are shifted
I8250_PARITY_ODD   = 20H
I8250_PARITY_EVEN  = 30H
I8250_PARITY_MARK  = 28H
I8250_PARITY_SPACE = 38H

;; masks for the MCR
I8250_MCR_DTR     = 1H      ;; activate DTR line
I8250_MCR_RTS     = 2H      ;; activate RTS line
I8250_MCR_OUT1    = 4H      ;; out1 Line
I8250_MCR_OUT2    = 8H      ;; out2 line
I8250_MCR_LOOP    = 10H     ;; loopback

;; masks for the LSR
I8250_LSR_DIN     = 1H      ;; data in read register
I8250_LSR_OVR     = 2H      ;; data overun
I8250_LSR_PERR    = 4H      ;; data parity error
I8250_LSR_FERR    = 8H      ;; data framing error
I8250_LSR_BREAK   = 10H     ;; break detected
I8250_LSR_DOUT    = 20H     ;; Transmit buffer empty
I8250_LSR_TSR     = 40H     ;; Transmit shift reg empty (no data on line)

;; masks for the MSR
I8250_MSR_DELTA_CTS   = 1H  ;; CTS changed
I8250_MSR_DELTA_DSR   = 2H  ;; DSR changed
I8250_MSR_DELTA_RI    = 4H  ;; RI changed
I8250_MSR_DELTA_DCD   = 8H  ;; DCD changed
I8250_MSR_CTS         = 10H ;; CTS active
I8250_MSR_DSR         = 20H ;; DSR active
I8250_MSR_RI          = 40H ;; RI active
I8250_MSR_DCD         = 80H ;; DCD active

;;*****************************************************************************
;; defs for the I8259 programable interupt controller

IBM_I8259    = 20H          ;; standard place on the IBM PC

I8259_REG_CNTRL       = 0   ;; the 8259 control register
I8259_REG_MASKS       = 1   ;; the interupt mask register

;; control register functions
I8259_CNTRL_EOI       = 20H ;; the End of Interupt command


;;*****************************************************************************
;;   I8250_DECLARE declares your intent to use a 8250 serial controler at
;;   address 'io_addr', using interupt 'irq'.  When it gets characters it calls
;;  <port_prefix>_CONSUME_in_AL_const_BX_BP_ES 'port' and
;;  <port_prefix>_WRITE_EMPTY_const_BX_CX_DX_BP_SI_DI_ES 'port' when it
;;  can write characters.  If 'flow' is non-blank and = 1
;;  then hardware flow control using RTS-CTS is followed.
;;
I8250_DECLARE MACRO name, port_prefix, port, io_addr, irq, flow
    .errb <name>
    .errb <irq>

    .DATA
    i8250_declared            = name
    i8250_&name&_port         = port
    i8250_&name&_prefix       equ <port_prefix>
    i8250_&name&_declared     = 1
    i8250_&name&_io           = io_addr
    i8250_&name&_irq          = irq

    i8250_&name&_flow         = 0
    ifnb <flow>
        i8250_&name&_flow     = 0&flow
    endif

    .CODE
    global i8250_data_seg:word
    global i8250_&name&_real_define_in_BX_out_AX:near
ENDM


;;******************************************************************************
;;   I8250_DEFINE name, fail
;;      sets asside memory an name object and initializes it.  This
;;      routine is a no-op if 'name' was not declared.  It jumps to 'fail'
;;      if there was an error in  setup.  BX contains the word that
;;      is the baud rate divisor.  (12 = 9600Baud, 6 = 19200Baud, etc)
;;
I8250_DEFINE_in_BX MACRO name, fail
   .errb <name>
   .errb <fail>

ifdef i8250_&name&_declared
    call i8250_&name&_real_define_in_BX_out_AX
    or AX, AX
    jnz fail
endif
ENDM

;;*************************************************************************
;; I8250_REAL_DEFINE is simply a the code that I8250_DEFINE jumps to.
;; this indirection is necessary to avoid macros getting too large.
;;
I8250_REAL_DEFINE MACRO name
    local done
    .errb <name>

ifdef i8250_&name&_declared
    i8250_&name&_real_define_in_BX_out_AX:

    mov word ptr CS:i8250_data_seg, DS      ;; make sure interupt routine OK

        ;; turn off my interupt
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8259_REG_MASKS, IBM_I8259
    and AL, (1 shl i8250_&name&_irq)
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8259_REG_MASKS, IBM_I8259

    I8250_SETUP_in_BX_out_AX name, done

        ;; turn on my interupt
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8259_REG_MASKS, IBM_I8259
    and AL, (not (1 shl i8250_&name&_irq))
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8259_REG_MASKS, IBM_I8259
    sti             ;; turn on interupts, if not already on

    xor AX, AX                          ;; return success
    done:
    ret

if i8250_declared eq name           ; define once for all

    ;;*****************************************************************
    ;; define the interupt handler
    .CODE
    i8250_data_seg: DW 0        ;; this location hold the data segment

    i8250_interupt:             ;; the actual interupt handler
    cli
    push DS
    push AX
    push CX
    push DX
    push SI
    push DI
    mov DS, word ptr CS:i8250_data_seg

    IRP idx, <1,2,3,4,5,6,7,8>      ;; check every chip
       I8250_IF_CHECK_const_BX_BP_ES idx
    endm

    mov AL, I8259_CNTRL_EOI             ; tell the 8259 we are done
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8259_REG_CNTRL, IBM_I8259
    pop DI
    pop SI
    pop DX
    pop CX
    pop AX
    pop DS
    iret                                ; interupts flag restored on return
endif
endif

ENDM


;;******************************************************************************
;; I8250_SETUP does all the 'per chip' setup for a 8250 serial chip associated
;; with 'name'.  if there is a failure 'fail' is jumped to, AX will have a
;; non-zero value if the 'fail' branch is taken.  BX contains the word that
;; is the baud rate divisor.  (12 = 9600Baud, 6 = 19200Baud)
;;
I8250_SETUP_in_BX_out_AX MACRO name, fail
    local done, is_a_16550AF, is_a_8250

ifdef i8250_&name&_declared
        ; check to see that a serial port is there by reading 8250 register
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_LSR, i8250_&name&_io
    cmp AL, 0FFH                ;; non-existant registers turn up as all 1s
    jz fail

        ;; set the baud rate divisor
    mov AL, I8250_LCR_DIVISOR
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8250_REG_LCR,i8250_&name&_io

    mov AX, BX                  ;; get the baud rate
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8250_REG_DIVL, i8250_&name&_io
    mov AL, AH
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8250_REG_DIVH,i8250_&name&_io

    mov AL, (8-5) + I8250_PARITY_IGN        ;; 8 bits no parity 1 stop bit
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8250_REG_LCR, i8250_&name&_io

    if i8250_&name&_flow eq 1
        mov AL, I8250_IER_DIN + I8250_IER_DOUT + I8250_IER_MODEM
    else
        mov AL, I8250_IER_DIN + I8250_IER_DOUT
    endif
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8250_REG_IER, i8250_&name&_io

        ;; Turn on FIFO mode if this is a 16550AF
    mov AL, NS16550_FIFO_ON+NS16550_FIFO_FIN+NS16550_FIFO_FOUT+NS16550_TRIG_8
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES NS16550_REG_FIFO,i8250_&name&_io

        ;; make sure that this is a 16550AF not just a 16550 (which has a bug)
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_IIR, i8250_&name&_io
    and AL, NS16550_IIR_CHECK
    test AL, 80H                    ;; is it a 16550?
    jz is_a_8250
    test AL, 40H                    ;; is it a 16550AF?
    jnz is_a_16550AF
        mov AL, 0                   ;; turn off FIFO, the 16550 is buggy
        WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES NS16550_REG_FIFO,i8250_&name&_io
    is_a_16550AF:
    is_a_8250:

        ;; set DTR and RTS for those modems that care
        ;; ON AN IBM PC OUT2 MUST BE SET FOR PROPER OPERATION
    mov AL, I8250_MCR_DTR + I8250_MCR_RTS + I8250_MCR_OUT2
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8250_REG_MCR, i8250_&name&_io

    cli
    xor AX, AX                  ;; load the interupt vector
    mov ES, AX
    mov DI, (i8250_&name&_irq+8)*4
    mov BX, offset i8250_interupt
    mov AX, CS
    mov ES:[DI], BX
    mov ES:[DI+2], AX
    sti

        ; acknowledge any interupts that may have occured in the past
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_RDR, i8250_&name&_io
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_MSR, i8250_&name&_io
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_IIR, i8250_&name&_io
endif
ENDM


;;******************************************************************************
;; I8250_IF_CHECK checks to see of interface 'name' has any characters to write
;; or to read and does the appropriate upcall if there is anthing to do.
;;
I8250_IF_CHECK_const_BX_BP_ES MACRO name
    local done, try_write, try_read, done_write

ifdef i8250_&name&_declared
    try_read:
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_LSR, i8250_&name&_io
    and AL, I8250_LSR_DIN               ;; is there a character ready?
    jz try_write

    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_RDR, i8250_&name&_io
    UPCALL_CONSUME_in_AL_const_BX_BP_ES %i8250_&name&_prefix, %i8250_&name&_port
    jmp try_read                        ;; keep trying until failure (for 16650)

    try_write:
        ; acknowledge the Tran Empty interupt
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_IIR, i8250_&name&_io

    I8250_CAN_WRITE_const_BX_CX_BP_SI_DI_ES name, done_write
       UPCALL_WRITE_EMPTY_const_BX_BP_ES %i8250_&name&_prefix,%i8250_&name&_port
    done_write:

        ;; have all the interupts been processed?
    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_IIR, i8250_&name&_io
    test AL, I8250_IIR_NOINT
    jz try_read                 ;; no, then try again until they are

        ;; Note that this final check for interupts is absolutely
        ;; necessary because the 8259 responds to EDGES, not LEVELs
        ;; only if we are absolutely sure the interupt line has gone
        ;; low (which would be the case if IIR has NOINT bit = 1) can
        ;; we be sure that the next interupt will generate an EDGE
        ;; the the 8259 will respond to.   Without this check it is
    ;; possible for interupts from the 8250 to be lost causing
    ;; the code to hang
    done:
endif
ENDM

UPCALL_CONSUME_in_AL_const_BX_BP_ES MACRO prefix, port
    prefix&_CONSUME_in_AL_const_BX_BP_ES port
ENDM

UPCALL_WRITE_EMPTY_const_BX_BP_ES MACRO prefix, port
    prefix&_WRITE_EMPTY_const_BX_BP_ES port
ENDM


;;******************************************************************************
;; W_CAN_WRITE jumps to 'not_ready' if the 8250 chip associated with
;; 'name' is not ready to recieve another byte.  Otherwise it just returns.
;;
I8250_CAN_WRITE_const_BX_CX_BP_SI_DI_ES MACRO name, not_ready
    .errb <name>
    .errb <success>

        ;; if we are doing flow control, we can only send if CTS is active
    if i8250_&name&_flow eq 1
        READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_MSR, i8250_&name&_io
        and AL, I8250_MSR_CTS
        jz not_ready
    endif

    READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_LSR, i8250_&name&_io
    and AL, I8250_LSR_DOUT              ;; is there a character ready?
    jz not_ready
ENDM


;;******************************************************************************
;; WRITE_in_AL writes the character in AL to the chip 'name'.  It
;; will busy wait if necessary, however this routine is guarenteed not
;; to busy wait if it is called only when the WRITE_EMPTY upcall is issued.
;;
I8250_WRITE_in_AL_const_BX_BP_ES MACRO name
    local wait_loop, ready
    .errb <name>

    mov SI, AX                              ;; save AL
    xor CX, CX
    wait_loop:
        READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES I8250_REG_LSR, i8250_&name&_io
        and AL, I8250_LSR_DOUT              ;; is there a character ready?
        jnz ready
        dec CX                              ;; so we don't wait forever
        jnz wait_loop

    ready:
    mov AX, SI                              ;; restore AL
    WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES I8250_REG_THR, i8250_&name&_io

ENDM


;;******************************************************************************
;; utility functions needed only within this module

READ_PORT_out_AL_const_BX_CX_BP_SI_DI_ES MACRO port, if_io
    mov DX, if_io+port
    in  AL, DX                              ;; AL contains data read from port
ENDM

;;******************************************************************************
WRITE_PORT_in_AL_const_AX_BX_CX_BP_SI_DI_ES MACRO port, if_io
    mov DX, if_io+port
    out DX, AL                              ;; AL contains data read from port
ENDM