Tech Arsenal 1/Tech Arsenal (Arsenal Computer).ISO/tek-05/drivers1.zip/82586.ASM

Assembly Source File | 1992-01-07 | 26KB | 997 lines

i82586_version    equ    2
  ifndef DAN
DAN    equ    4            ; 4 seems to work best.
  endif

;
; Code that is common between 82586 implementations.
;

; Ported from Tim Krauskopf's micnet.asm, an assembly language
; driver for the MICOM-Interlan NI5210, by Russell Nelson.  Any bugs
; are due to Russell Nelson.
; Updated to version 1.08 Feb. 17, 1989 by Russell Nelson.
; Updated to support 1500 byte MTU April 27, 1989 By Brad Clements.

; Copyright, 1988-1992, Russell Nelson, Crynwr Software

;   This program is free software; you can redistribute it and/or modify
;   it under the terms of the GNU General Public License as published by
;   the Free Software Foundation, version 1.
;
;   This program is distributed in the hope that it will be useful,
;   but WITHOUT ANY WARRANTY; without even the implied warranty of
;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;   GNU General Public License for more details.
;
;   You should have received a copy of the GNU General Public License
;   along with this program; if not, write to the Free Software
;   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

;
;  Structure elements specific to the Intel 82586 chip
;

; System Configuration Pointer
scp_struc    struc
scp_bus        db    ?,?,?, ?,?,?    ; bus use flag (0=16 bit, 1=8 bit).
scp_ptr        dd    ?        ; 24pointer to iscp
scp_struc    ends

; Intermediate System Configuration Pointer
iscp_struc    struc
iscp_busy    db    ?,?        ; busy flag (zeroed after init).
iscp_offset    dw    ?        ; 16pointer to iscp
iscp_base    dd    ?        ; base for all 16 pointers, lo, hi
iscp_struc    ends

; System Control Block
scb_struc    struc
scb_stat    dw    ?        ; status
scb_com        dw    ?        ; command
scb_cbl        dw    ?        ; 16pointer to command block list
scb_rfa        dw    ?        ; 16pointer to receive frame list
scb_serrs    dw    4 dup(?)    ; 4 words of error counts
scb_struc    ends

; (Received) Frame Descriptor
fd_struc    struc
fd_status    dw    ?        ; status word for frame
fd_eol        dw    ?        ; end of FD list flag
fd_link        dw    ?        ; 16pointer to next FD
fd_ptr        dw    ?        ; 16pointer to list of RBD's
fd_dest        db    EADDR_LEN dup(?); 48 bits of destination
fd_source    db    EADDR_LEN dup(?); 48 bits of source
fd_cnt        dw    ?        ; length field of frame.
fd_struc    ends

; Receive Buffer Descriptor
rbd_struc    struc
rbd_status    dw    ?        ; status word in RBD
rbd_link    dw    ?        ; 16pointer to next RBD
rbd_ptr        dd    ?        ; 24pointer to actual buffer
rbd_size    dw    ?        ; size of the buffer
rbd_struc    ends

; Transmit Command Block
tcb_struc    struc
tcb_status    dw    ?        ; status word for xmit
tcb_com        dw    ?        ; command to transmit
tcb_link    dw    ?        ; 16pointer to next command
tcb_ptr        dw    ?        ; 16pointer to xmit TBD
tcb_addr    db    EADDR_LEN dup(?); destination address
tcb_len        dw    ?
tcb_struc    ends

; Transmit Buffer Descriptor
tbd_struc    struc
tbd_status    dw    ?        ; bit 15=EOF, 13-0=actual count
tbd_link    dw    ?        ; 16pointer to next TBD
tbd_ptr        dd    ?        ; 24pointer to buffer
tbd_struc    ends

; all commands have at least the following:
cmd_struc    struc
cmd_status    dw    ?        ; status word
cmd_com        dw    ?        ; command word.
cmd_struc    ends

; MC-SETUP Command Block
mcb_struc    struc
mcb_status    dw    ?        ; status word for multicast
mcb_com        dw    ?        ; command to setup multicast
mcb_link    dw    ?        ; 16pointer to next command
mcb_cnt        dw    ?        ; number of multicast addresses.
mcb_struc    ends

; TDR Command Block
tdr_struc    struc
tdr_status    dw    ?        ; status word for TDR
tdr_com        dw    ?        ; command to setup TDR
tdr_link    dw    ?        ; 16pointer to next command
tdr_time    dw    ?        ; error bits and time
tdr_struc    ends

;Memory allocation.

SCPTR    EQU    0fff6h            ; hardwired address for SCP
ISCPTR    EQU    0ffeeh            ; my address for ISCP, points to SCB
SCB    EQU    ISCPTR - 16        ; system control block base
CCBPTR    EQU    SCB - 18        ; offset of configure command block
TBDPTR    EQU    CCBPTR - 8        ; xmit BD offset
TCBPTR    EQU    TBDPTR - 16        ; xmit CB offset
TBUFPTR    EQU    TCBPTR - GIANT        ; xmit buffer offset
;the receive buffers appear at lower addresses than TBUFPTR.
RBUFLEN    EQU    200
RBUF_TOTAL    equ    (size fd_struc) + (size rbd_struc) + RBUFLEN
FDBASE        equ    TBUFPTR - RBUF_TOTAL

memory_begin    dw    ?

    public    rcv_modes
rcv_modes    dw    7        ;number of receive modes in our table.
        dw    0               ;There is no mode zero
        dw    0
        dw    rcv_mode_2
        dw    rcv_mode_3
        dw    rcv_mode_4    ;haven't set up perfect filtering yet.
        dw    0
        dw    rcv_mode_6

firstfd        dw    FDBASE        ; start of FD queue
lastfd        dw    0        ; end of the FD chain
lastbd        dw    0        ; end of the BD chain
flag        dw    0


;
; Configuration block for 82586, this comprises one config command
;  Parameters taken from MICOM driver
;
CBCONF    DW    0        ; status word
    DW    8002H        ; end of command list + configure command
    DW    0ffffh        ; link to next command (not used)
    DW    080CH        ; fifo=8, byte count=C
    DW    2E00H        ; important! Addr (AL) not inserted on the fly!
    DW    6000H        ; IFS = 60h
    DW    0F200H        ; retry=F, slot time=200h
CBCONF_FLAGS    label    byte
    DW    0        ; flags, set to 1 for promiscuous
CBCONF_MINLEN    label    byte
    DW    40H        ; min frame length=40h


doca_wait:
;enter with ax = command to execute, es = base_addr.
;exit with nc if the command ran to completion.
;exit with cy if the command timed out.  Eventually we'll also reset the chip.
    mov    es:[SCB].scb_com,ax    ;set the command.

    mov    si,es:[SCB].scb_cbl    ;
    mov    es:[si].cmd_status,0    ; status word of specific command
    and    ax,0700h
    cmp    ax,0100h        ; is it an action command?
    jne    doca_wait_a        ; no, any other

    call    doca

comment \
Quoting from the D-Step Errata Revision 2.0:

The value for the deadman timer should be greater than the longest
command execution time.  The command which can take the longest time
to execute is the transmit command, assuming maximum retries.  To
determine the maximum amount of time the transmit command may take,
one must use the following equation: 7143 ST + 14 f, where ST stands
for Slot Time and f = Maximum Frame Size + IFS + Preamble.  For
Ethernet/IEEE 802.3 where ST = 512 bits, f = 12144 bits, Preamble =
64 bits, IFS  96 bits, and one bit = 0.1 usec, the deadman timeout
should be greater than 0.369 seconds.

\

    mov    ax,14            ;36.4 ticks / seconds * .369 seconds
    call    set_timeout
doca_wait_1:
    test    es:[si].cmd_status,8000h    ; is command complete?
    jnz    doca_wait_2        ;yes.
    call    do_timeout        ;did we time out yet?
    jne    doca_wait_1        ;not yet.
;reset the chip here, then Configure, IA-Setup, and MC-Setup.
    stc                ;timeout -- uh-oh.
    ret
doca_wait_2:
    clc
    ret

doca_wait_a:
    call    doca
doca_wait_a_0:
    cmp    es:[SCB].scb_com,0    ; has the command been accepted?
    jnz    doca_wait_a_0        ; not yet.
    clc
    ret


    include    timeout.asm
    include    movemem.asm

    public    as_send_pkt
; The Asynchronous Transmit Packet routine.
; Enter with es:di -> i/o control block, ds:si -> packet, cx = packet length,
;   interrupts possibly enabled.
; Exit with nc if ok, or else cy if error, dh set to error number.
;   es:di and interrupt enable flag preserved on exit.
as_send_pkt:
    ret

    public    drop_pkt
; Drop a packet from the queue.
; Enter with es:di -> iocb.
drop_pkt:
    assume    ds:nothing
    ret

    public    xmit
; Process a transmit interrupt with the least possible latency to achieve
;   back-to-back packet transmissions.
; May only use ax and dx.
xmit:
    assume    ds:nothing
    ret


    public    send_pkt
send_pkt:
;enter with es:di->upcall routine, (0:0) if no upcall is desired.
;  (only if the high-performance bit is set in driver_function)
;enter with ds:si -> packet, cx = packet length.
;exit with nc if ok, or else cy if error, dh set to error number.
    assume    ds:nothing
    mov    es,base_addr        ; base for board

    cmp    cx,GIANT        ; Is this packet too large?
    ja    send_pkt_toobig

    mov    dx,cx            ; save a copy, might be less than 60, ok

    cmp    dx,RUNT            ; minimum length for Ether
    jnb    oklen
    mov    dx,RUNT            ; make sure size at least RUNT
oklen:
    mov    di,TBUFPTR        ; start of xmit buffer

;
;  check for previous xmit
;
xwait:
    mov    bx,es:[SCB].scb_com    ; has previous command been accepted?
    or    bx,bx
    jnz    xwait            ; not there yet, wait for it
wait_for_transmit_to_complete:
    test    word ptr es:[TCBPTR],4000h
    jnz    wait_for_transmit_to_complete
;
;  move the data using word moves.
;
    call    movemem
;
;  put the correct size into the TBD
;
    or    dx,08000h            ; end of frame bit flag
    mov    es:[TBDPTR].tbd_status,dx    ; store it
    mov    es:[TCBPTR].tcb_status,0    ; zero status wd
    mov    es:[TCBPTR].tcb_com,8004h    ; xmit command in TCB
    mov    es:[SCB].scb_com,0100h        ; execute command
    mov    es:[SCB].scb_cbl,TCBPTR    ; say where xmit command is

    call    doca

    clc
    ret
send_pkt_toobig:
    mov    dh,NO_SPACE
    stc
    ret


rcv_mode_2:
    and    CBCONF_FLAGS,not 3
    or    CBCONF_FLAGS,2        ;disable broadcasts.
    mov    CBCONF_MINLEN,40h
    jmp    short reconfigure
rcv_mode_4:
rcv_mode_3:
    and    CBCONF_FLAGS,not 3    ;clear promiscuous mode.
    mov    CBCONF_MINLEN,40h
    jmp    short reconfigure
rcv_mode_6:
    and    CBCONF_FLAGS,not 3
    or    CBCONF_FLAGS,1        ;set promiscuous mode.
    mov    CBCONF_MINLEN,0        ;allow runts.
reconfigure:
    mov    es,base_addr        ;get the base address for the board.
    mov    si,offset CBCONF    ; configure command
    mov    di,CCBPTR        ; where command will reside
    mov    cx,9
    rep    movsw            ; copy to board
;
;  issue the configure command
;
    mov    es:[SCB].scb_cbl,CCBPTR    ; where conf command is
    mov    es:[SCB].scb_serrs[0],0    ; zero errs field
    mov    es:[SCB].scb_serrs[2],0    ; zero errs field
    mov    es:[SCB].scb_serrs[4],0    ; zero errs field
    mov    es:[SCB].scb_serrs[6],0    ; zero errs field
    mov    ax,100h            ; do-command command
    call    doca_wait
    ret


    public    set_multicast_list
set_multicast_list:
;enter with ds:si ->list of multicast addresses, cx = number of addresses.
;return nc if we set all of them, or cy,dh=error if we didn't.
    assume    ds:code
    mov    es,base_addr
    mov    es:[SCB].scb_cbl,TBUFPTR    ;use the transmit buffer.

    mov    es:[TBUFPTR].mcb_status,0    ;status word
    mov    es:[TBUFPTR].mcb_com,08003h    ;command word for mc-setup + EL
    mov    es:[TBUFPTR].mcb_link,-1    ;no command link.
    mov    di,TBUFPTR + mcb_cnt
    mov    ax,cx            ;store the count.
    stosw
    rep    movsb

comment \ avoid deferred execution of a CU command during reception.
If a command is executed with a length of 18 to 20 bytes, and a frame
is received, the 82586 may deadlock with HOLD active.  We avoid this
problem by suspending the receiver. \

    mov    ax,30h            ;suspend frame receiving.
    call    doca_wait

    mov    ax,100h            ; do-command command
    call    doca_wait
    jnc    set_multicast_2

    mov    ax,20h            ;resume frame receiving.
    call    doca_wait

    mov    dh,NO_MULTICAST        ;for some reason we can't do multi's.
    stc
    ret
set_multicast_2:
    mov    ax,20h            ;resume frame receiving.
    call    doca_wait

    clc
    ret


    public    terminate
terminate:
    assume    ds:code
    ret

    public    reset_interface
reset_interface:
;reset the interface.
;we don't do anything.
    assume    ds:nothing
    ret


;called when we want to determine what to do with a received packet.
;enter with cx = packet length, es:di -> packet type, dl = packet class.
    extrn    recv_find: near

;called after we have copied the packet into the buffer.
;enter with ds:si ->the packet, cx = length of the packet.
    extrn    recv_copy: near

    extrn    count_in_err: near
    extrn    count_out_err: near

    public    recv
recv:
  ifdef IO_INTCLR
    loadport            ;clear the interupt latch.
    setport    IO_INTCLR
    out    dx,al
  endif

    mov    flag, 1
;called from the recv isr.  All registers have been saved, and ds=cs.
;Upon exit, the interrupt will be acknowledged.
recv1:
    mov    ds,base_addr    ; base for board
    assume    ds:nothing

    mov    ax,ds:[SCB].scb_stat    ;get the status.
recv_isr_1:
    cmp    ds:[SCB].scb_com,0    ;has previous command been accepted?
    jne    recv_isr_1        ;no -- keep waiting.

    and    ax,0f000h        ;isolate the ACK bits to make a
                    ;  command to ack the interrupt.
  if DAN and 1
    jz    recv_isr_2
  endif

    mov    ds:[SCB].scb_com,ax    ;set the command.
    call    doca
recv_isr_2:
    cmp    ds:[SCB].scb_com,0    ; has the command been accepted?
    jnz    recv_isr_2        ; not yet.

;  Get whatever packets are on the board
;
    mov    bx,firstfd    ; get addr of first FD in list
    mov    ax,[bx].fd_status    ; status word of frame
    test    ax,08000h    ; frame written?
    jnz    okframe

    jmp    ru_start    ; no, restore receiver if necessary
frame_bad:
    call    count_in_err
ptrupdate_j_1:
    jmp    ptrupdate

;  we have a frame, read it in
;
okframe:
    test    ax,02000h        ;check frame OK bit
    jz    frame_bad        ;bad, fix it.
    mov    si,[bx].fd_ptr        ;get pointer to buffer descriptor
    xor    cx,cx            ;start with zero bytes.
countbuf:                ;es:di is already set to receive packet
    mov    dx,si            ;save a copy of current BD ptr
    mov    ax,[si].rbd_status    ;get status and count word for BD
    test    ax,04000h        ;is count field there?
    jz    ptrupdate_j_1        ;no - we give up here.
    add    cl,al            ;add the count into cx.
    adc    ch,0
    mov    si,[si].rbd_link    ;go to next BD in list
    test    ax,8000h        ;is this the last frame?
    je    countbuf        ;no - keep counting.

    push    bx
    push    cx

    mov    ax,cs            ;we need ds = code.
    mov    ds,ax
    assume    ds:code

    mov    es,base_addr        ;get a pointer to their type.
    mov    di,es:[bx].fd_ptr    ;get pointer to buffer descriptor
    mov    di,es:[di].rbd_ptr.offs    ;get offset of data
    add    di,EADDR_LEN+EADDR_LEN    ;skip the ethernet addreses and
                    ;  point to the packet type.

    mov    dl, BLUEBOOK        ;assume bluebook Ethernet.
    mov    ax, es:[di]
    xchg    ah, al
    cmp     ax, 1500
    ja    BlueBookPacket
    inc    di            ;set di to 802.2 header
    inc    di
    mov    dl, IEEE8023
BlueBookPacket:
    call    recv_find        ;look up our type.

    pop    cx
    pop    bx
    mov    ds,base_addr        ;restore ds to the board.
    assume    ds:nothing

    mov    ax,es            ;is this pointer null?
    or    ax,di
    je    ptrupdate        ;yes - just free the frame.

    push    cx
    push    es            ;remember where the buffer pointer is.
    push    di
  if DAN and 2
    push    cx
  endif

    mov    si,[bx].fd_ptr        ;get pointer to buffer descriptor
copybuf:
    mov    dx,si            ;save a copy of current BD ptr
    xor    ch,ch            ;200 bytes is largest this can be
    mov    cl,byte ptr [si].rbd_status;get count word for BD
    mov    si,[si].rbd_ptr.offs    ;get offset of data
  if DAN and 2
    pop    ax
    sub    ax, cx
    jc    copydone
    push    ax
  ENDIf
    call    movemem
    mov    si,dx            ;get back current BD ptr
    test    [si].rbd_status,8000h    ;check EOF bit
    mov    si,[si].rbd_link    ;go to next BD in list
    jz    copybuf            ;not done, keep copying it.

  if DAN and 2
    pop    cx
copydone:
  endif
    pop    si            ;now give the frame to the client.
    pop    ds
    pop    cx
    assume    ds:nothing

    call    recv_copy
;
;  we are done with the frame, do the list management
;
ptrupdate:
    push    cs
    pop    ds
    assume    ds:code
    mov    es,base_addr        ; reload board segment

    mov    si,es:[bx].fd_ptr    ; first BD in frame list
nextbd:
    mov    cx,es:[si].rbd_status    ; count word for BD, EOF bit
    test    cx,08000h        ; EOF bit, if set, save si in lastbd
    jnz    dolastbd
    mov    es:[si].rbd_status,0    ; clear status word, EOF bit
    cmp    si,lastbd        ; see if we are wrapping
    jz    dolastbd        ; yes, just undo it
    mov    si,es:[si].rbd_link    ; follow link
    jmp    nextbd
dolastbd:
    mov    di,lastbd        ; where end of BD list is now
    mov    lastbd,si        ; store last known BD
    mov    es:[si].rbd_size,08000h+200; end of list here
    mov    es:[si].rbd_status,0    ; clear status word, EOF bit
; size field for not end of list
    mov    es:[di].rbd_size,200    ; remove old end-of-list

;
;  update the FD list flags, new end-of-list
;
    mov    es:[bx].fd_eol,08000h    ; store new EOL
    mov    es:[bx].fd_status,0    ; clear status word for frame
    mov    di,lastfd        ; get old end-of-list
    mov    es:[di].fd_eol,0    ; zero old one
    mov    lastfd,bx        ; update stored pointer
    mov    si,es:[bx].fd_link    ; where next fd is
    mov    firstfd,si        ; store that info for next time
  if DAN and 4
    jmp    recv1
  endif

ru_start:
; re-start receive unit
;
;  check to see if the receiver went off because of no resources
;  and restart receiver if necessary
;
    push    cs
    pop    ds
    mov    es,base_addr
    mov    ax,es:[SCB].scb_stat    ; status word for SCB
    and    ax,070h        ; receiver status
    cmp    al,020h        ; receiver has no resources
    jnz    hasres
  if DAN and 8
    cmp    flag, 1
    jnz    ru_start1
    mov    flag, 0
    jmp    recv1
  endif

ru_start1:
    call    count_out_err
;
;  setup lists for starting the RU on the chip
;  we know that there isn't anything in the buffer that we want
;

    mov    bx,firstfd        ; get first FD on free list (assume free)
    mov    es:[SCB].scb_rfa,bx    ; put into SCB
    mov    si,lastbd        ; pointer to a BD, end of chain
    mov    ax,es:[si].rbd_link    ; pointer to next BD
    mov    es:[bx].fd_ptr,ax    ; set to start of BDs
;
;
;  Start the RU, doesn't need CB, only SCB parms.
;   command, to start receiving again
;
    mov    ax,10h            ; start RU
    call    doca_wait
hasres:
;I don't we need to wait here because we haven't done anything to wait for.
    ret


    public    recv_exiting
recv_exiting:
;called from the recv isr after interrupts have been acknowledged.
;Only ds and ax have been saved.
    assume    ds:nothing
    ret


    public    set_address
set_address:
    assume    ds:nothing
;enter with ds:si -> Ethernet address, CX = length of address.
;exit with nc if okay, or cy, dh=error if any errors.
    cmp    cx,EADDR_LEN        ;ensure that their address is okay.
    je    set_address_4
    mov    dh,BAD_ADDRESS
    stc
    jmp    short set_address_done
set_address_4:

;  Next step, load our address into the board
;     reuses the space that the configure command used, with different command
;
    mov    es,base_addr        ; set to base address
    mov    es:[SCB].scb_cbl,CCBPTR    ; say where conf command is

    mov    di,CCBPTR        ; start of config command block
    xor    ax,ax
    stosw                ; zero status word for commmand
    mov    ax,8001h        ; IA setup command + EL
    stosw
    xor    ax,ax
    dec    ax
    stosw                ; set link value to -1 (unused)

    rep    movsb            ; move their ethernet address in.
;
;  start the IA setup command
;
    mov    ax,100h            ; do-command command
    call    doca_wait
    jnc    set_address_okay
    mov    dh,-1            ; no error in the list applies.
    jmp    short set_address_done
set_address_okay:
    mov    cx,EADDR_LEN        ;return their address length.
    clc
set_address_done:
    push    cs
    pop    ds
    assume    ds:code
    ret


end_resident    label    byte

timeout_msg    db    "Timed out while initializing the board.",CR,LF,'$'
our_address    db    6 dup(?)    ;temporarily hold our address

addr_bad_msg    db    "Invalid memory address.",CR,LF,'$'

  if 0
tdr_warn_msg    db    "TDR: ",'$'
tdr_ok_msg    db    "Ok",CR,LF,'$'
tdr_none_msg    db    "Ethernet card doesn't seem to be plugged in.",CR,LF,'$'
tdr_open_msg    db    " clocks away is an OPEN (not completely reliable)",CR,LF,'$'
tdr_short_msg    db    " clocks away is a SHORT (not completely reliable)",CR,LF,'$'
  endif

mem8_16        db    2        ; 1 for 16k, 2 for 8k

    extrn    set_recv_isr: near
    extrn    maskint: near

;enter with si -> argument string, di -> word to store.
;if there is no number, don't change the number.
    extrn    get_number: near

;enter with dx -> name of word, di -> dword to print.
    extrn    print_number: near

;enter with ax = number to print.
    extrn    decout: near

timeout_error:
    mov    dx,offset timeout_msg
    jmp    short error
error:
    mov    ah,9
    int    21h
    stc
    ret

;
;  data for configuring and setting up the board
;
;  chip always looks at SCP for config info which points to ISCP for the
;  pointer to the CONTROL BLOCK which handles everything from there.
;  Kind of indirect, but it works.
;
SCP    DB    0            ; bus use flag (0=16 bit, 1=8 bit).

    public    etopen
etopen:
    mov    al,int_no
    call    maskint            ;disable these interrupts.

    cmp    base_addr.offs,0    ;low word of segment can't be zero.
    je    etopen_1
    cmp    base_addr.segm,0    ;high word of segment must be zero.
    je    etopen_2
etopen_1:
    mov    dx,offset addr_bad_msg
    mov    ah,9
    int    21h

    stc
    ret
etopen_2:

;  Initialize the Ethernet board, set receive type.
;
;  check for correct EPROM location
;
    call    check_board

;
;  Turn off interrupts, I don't want them
;
  ifdef IOINTOF
    loadport
    setport IOINTOF
    out    dx,al
  endif
;
;  Disconnect from network
;
  ifdef IODIS
    loadport
    setport    IODIS
    out    dx,al
  endif

;
;  Initialize the Ethernet board.
;
    sub    base_addr,0e00h
    mov    di,0e000h        ;our initial base address.
    mov    si,ISCPTR-2        ;try the init down a little.

;
;  Now discern the end of memory by repeatedly re-initializing the board
;  until the BUSY flag in the ISCP gets reset.
;
re_discern:
    mov    es,base_addr        ;remember where we think it starts.
    call    init_root        ;did we find our memory size?
    jc    confng            ;no, keep trying.
    inc    si            ;yes, see if we found the real one.
    inc    si
    call    init_root        ;try initializing it in a different locn.
    jnc    confok            ;it worked!  we've found the root.
    dec    si            ;it didn't work, keep trying.
    dec    si
confng:
    or    di,di            ;did we try all 64K?
    je    confbad            ;yes.

    add    base_addr,200h        ;advance the segment by 2000h bytes.
    sub    di,2000h        ;retreat the offset by 2000h bytes.
    jmp    re_discern        ;try this next higher address.
confbad:
    sti
    jmp    timeout_error

confok:
    mov    memory_begin,di
    call    reconfigure
    jc    confbad

;
;  Ask the board for the Ethernet address, and then use set_address to set it.
;
    push    ds
    pop    es
    mov    di,offset our_address
    mov    cx,EADDR_LEN
    call    get_address

    mov    si,offset our_address
    mov    cx,EADDR_LEN
    call    set_address
    jnc    store_address_2
    sti
    jmp    timeout_error
store_address_2:
;
;  IA sent, setup all of the other data structures on the board
;  start with xmit command descriptors
;
    mov    di,TCBPTR
    mov    es:[di].tcb_status,0
    mov    es:[di].tcb_com,08004h
    mov    es:[di].tcb_link,-1
    mov    es:[di].tcb_ptr,TBDPTR

    add    di,(size tcb_struc)

    mov    es:[di].tbd_status,0
    mov    es:[di].tbd_link,0
    mov    es:[di].tbd_ptr.offs,TBUFPTR
    mov    es:[di].tbd_ptr.segm,0

; Note that we allocate fd's, rbd's, and buffers all at the same time.  This
; doesn't mean that each pair of fd's and rbd's necessarily have anything to
; do with each other.  We just allocate them together because we want to have
; the same number of each, and it's easier to compute that way.

    mov    di,TBUFPTR        ;get the last buffer.

    mov    ax,di            ;compute the amount of free memory.
    sub    ax,memory_begin
    xor    dx,dx
    mov    bx,RBUF_TOTAL        ;each buffer takes this much.
    div    bx
    mov    cx,ax            ;put the number of buffers into cx.

init_rbuff_0:
    sub    di,RBUF_TOTAL        ;back the pointer down by a little.

;init the FD.
    mov    es:[di].fd_status,0
    mov    es:[di].fd_eol,0
    mov    es:[di].fd_ptr,-1
    lea    ax,[di]-RBUF_TOTAL    ;get the address of the next buffer.
    mov    es:[di].fd_link,ax

;init the BD.
    lea    bx,[di + (size fd_struc)]
    mov    es:[bx].rbd_status,0
    lea    ax,[bx-RBUF_TOTAL]    ;make a pointer to the next BD
    mov    es:[bx].rbd_link,ax
    lea    ax,[bx+(size rbd_struc)]    ;make a pointer to the buffer.
    mov    es:[bx].rbd_ptr.offs,ax
    mov    es:[bx].rbd_ptr.segm,0
    mov    es:[bx].rbd_size,RBUFLEN    ;length of the buffer.

    loop    init_rbuff_0

init_rbuff_1:
;patch the parameters of the last FD and BD so they link around to the head.
    mov    es:[di].fd_eol,8000h
    mov    es:[di].fd_link,FDBASE
    mov    lastfd,di

    lea    bx,[di + (size fd_struc)]
    mov    es:[bx].rbd_link,FDBASE + (size fd_struc)
    mov    es:[bx].rbd_size,RBUFLEN + 8000h
    mov    lastbd,bx

;now put the location of the first rbd into the first fd.
    mov    es:[FDBASE].fd_ptr,FDBASE  + (size fd_struc)

    call    enable_network

  if 0    ;this message only confuses users.

    mov    dx,offset tdr_warn_msg    ;warn them that the 82586 TDR sucks.
    mov    ah,9
    int    21h

;
; Test to see if the network is okay.
;
    mov    di,CCBPTR        ; start of config command block
    xor    ax,ax            ; zero status word for commmand
    stosw
    mov    ax,8005h        ; TDR command + EL
    stosw
    xor    ax,ax
    dec    ax
    stosw                ; set link value to -1 (unused)
    inc    ax
    stosw                ; zero time result.

    mov    ax,100h            ; do-command command
    call    doca_wait
    jnc    do_tdr_2        ; finished okay.
    mov    ax,2000h        ; treat a timeout as an open
    jmp    short do_tdr_5
do_tdr_2:
    mov    ax,word ptr es:[CCBPTR].tdr_time
do_tdr_5:
    mov    dx,offset tdr_ok_msg
    test    ax,8000h
    jne    do_tdr_3
    mov    dx,offset tdr_short_msg
    test    ax,2000h
    je    do_tdr_4
    mov    dx,offset tdr_none_msg
    cmp    ax,2000h
    je    do_tdr_3
    mov    dx,offset tdr_open_msg
do_tdr_4:
    push    dx
    and    ax,2048-1
    xor    dx,dx
    call    decout
    pop    dx
do_tdr_3:
    mov    ah,9
    int    21h
  endif

;
;  Start the RU, doesn't need CB, only SCB parms.
;   command, to start receiving
;
    mov    es:[SCB].scb_rfa,FDBASE    ; set to frame descriptors
    mov    ax,10h            ; start RU
    call    doca_wait
;
; Now reset CX, FR, CNA, and RNR so that we don't get a spurious interrupt.
;
    mov    ax,es:[SCB].scb_stat    ;get the status.
    and    ax,0f000h        ;isolate the ACK bits.
    mov    es:[SCB].scb_com,ax    ;make a command to
                    ;acknowledge the interrupt.
    call    doca
;
; Now hook in our interrupt
;
    call    set_recv_isr

    sti

    mov    al, int_no        ; Get board's interrupt vector
    add    al, 8
    cmp    al, 8+8            ; Is it a slave 8259 interrupt?
    jb    set_int_num        ; No.
    add    al, 70h - 8 - 8        ; Map it to the real interrupt.
set_int_num:
    xor    ah, ah            ; Clear high byte
    mov    int_num, ax        ; Set parameter_list int num.

    mov    dx,offset end_resident
    clc
    ret


init_root:
;enter with es:di -> beginning of our system memory window,
;  si -> place to put ISC.
;exit with nc if it worked, cy if it didn't work.

    mov    al,SCP
    mov    es:[SCPTR].scp_bus,al
    mov    es:[SCPTR].scp_ptr.offs,si
    mov    es:[SCPTR].scp_ptr.segm,0

    mov    es:[si].iscp_busy,1        ;set busy bit.
    mov    es:[si].iscp_offset,SCB        ;point to the SCB.
    mov    es:[si].iscp_base.offs,0    ;scb base.
    mov    es:[si].iscp_base.segm,0    ;scb base.

    call    reset_586        ; reset the 586, hardware-specific.

;
;  Issue a CA to initialize the chip after reset
;
    call    doca

    mov    ax,2            ;don't wait too long.
    call    set_timeout
init_root_2:
    cmp    es:[si].iscp_busy,0    ;did it clear the busy flag?
    je    init_root_1        ;yes.
    call    do_timeout
    jne    init_root_2
    stc
    ret
init_root_1:
    clc
    ret