kolibrios/kernel/branches/Kolibri-acpi/network/eth_drv/drivers/rtl8029.inc

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;                                                                 ;;
;; Copyright (C) KolibriOS team 2004-2007. All rights reserved.    ;;
;; Distributed under terms of the GNU General Public License       ;;
;;                                                                 ;;
;;  RTL8029.INC                                                    ;;
;;                                                                 ;;
;;  Ethernet driver for Menuet OS                                  ;;
;;                                                                 ;;
;;  Version 0.2  31 July 2002                                      ;;
;;                                                                 ;;
;;  This driver is based on the ns8390 driver from                 ;;
;;  the etherboot 5.0.6 project. The copyright statement is        ;;
;;                                                                 ;;
;;          GNU GENERAL PUBLIC LICENSE                             ;;
;;             Version 2, June 1991                                ;;
;;                                                                 ;;
;;  remaining parts Copyright 2002 Mike Hibbett,                   ;;
;;   mikeh@oceanfree.net                                           ;;
;;                                                                 ;;
;;  See file COPYING for details                                   ;;
;;                                                                 ;;
;;  While this implementation handles only PCI bus RTL8029         ;;
;;  hardware, it can be easily adapted to other NE2000 clone       ;;
;;  products. I just dont have any to try!                         ;;
;;                                                                 ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

$Revision$


;********************************************************************
;   Interface
;      rtl8029_reset
;      rtl8029_probe
;      rtl8029_poll
;      rtl8029_transmit
;
;********************************************************************




;**************************************************************************
; 8390 Register Definitions
;**************************************************************************
D8390_P0_COMMAND    equ    0x00
D8390_P0_PSTART     equ    0x01
D8390_P0_PSTOP      equ    0x02
D8390_P0_BOUND      equ    0x03
D8390_P0_TSR        equ    0x04
D8390_P0_TPSR       equ    0x04
D8390_P0_TBCR0      equ    0x05
D8390_P0_TBCR1      equ    0x06
D8390_P0_ISR        equ    0x07
D8390_P0_RSAR0      equ    0x08
D8390_P0_RSAR1      equ    0x09
D8390_P0_RBCR0      equ    0x0A
D8390_P0_RBCR1      equ    0x0B
D8390_P0_RSR        equ    0x0C
D8390_P0_RCR        equ    0x0C
D8390_P0_TCR        equ    0x0D
D8390_P0_DCR        equ    0x0E
D8390_P0_IMR        equ    0x0F
D8390_P1_COMMAND    equ    0x00
D8390_P1_PAR0       equ    0x01
D8390_P1_PAR1       equ    0x02
D8390_P1_PAR2       equ    0x03
D8390_P1_PAR3       equ    0x04
D8390_P1_PAR4       equ    0x05
D8390_P1_PAR5       equ    0x06
D8390_P1_CURR       equ    0x07
D8390_P1_MAR0       equ    0x08

D8390_COMMAND_PS0   equ    0x0       ;  Page 0 select
D8390_COMMAND_PS1   equ    0x40      ;  Page 1 select
D8390_COMMAND_PS2   equ    0x80      ;  Page 2 select
D8390_COMMAND_RD2   equ    0x20      ;  Remote DMA control
D8390_COMMAND_RD1   equ    0x10
D8390_COMMAND_RD0   equ    0x08
D8390_COMMAND_TXP   equ    0x04      ;  transmit packet
D8390_COMMAND_STA   equ    0x02      ;  start
D8390_COMMAND_STP   equ    0x01      ;  stop

D8390_COMMAND_RD2_STA     equ 0x22
D8390_COMMAND_RD2_STP     equ 0x21
D8390_COMMAND_RD1_STA     equ 0x12
D8390_COMMAND_RD0_STA     equ 0x0A
D8390_COMMAND_PS0_RD2_STP equ 0x21
D8390_COMMAND_PS1_RD2_STP equ 0x61
D8390_COMMAND_PS0_RD2_STA equ 0x22
D8390_COMMAND_PS0_TXP_RD2_STA equ 0x26

D8390_RCR_MON      equ    0x20      ;  monitor mode

D8390_DCR_FT1      equ    0x40
D8390_DCR_LS       equ    0x08      ;  Loopback select
D8390_DCR_WTS      equ    0x01      ;  Word transfer select

D8390_DCR_FT1_LS       equ   0x48
D8390_DCR_WTS_FT1_LS   equ   0x49

D8390_ISR_PRX      equ    0x01      ;  successful recv
D8390_ISR_PTX      equ    0x02      ;  successful xmit
D8390_ISR_RXE      equ    0x04      ;  receive error
D8390_ISR_TXE      equ    0x08      ;  transmit error
D8390_ISR_OVW      equ    0x10      ;  Overflow
D8390_ISR_CNT      equ    0x20      ;  Counter overflow
D8390_ISR_RDC      equ    0x40      ;  Remote DMA complete
D8390_ISR_RST      equ    0x80      ;  reset

D8390_RSTAT_PRX      equ    0x01      ;  successful recv
D8390_RSTAT_CRC      equ    0x02      ;  CRC error
D8390_RSTAT_FAE      equ    0x04      ;  Frame alignment error
D8390_RSTAT_OVER     equ    0x08      ;  FIFO overrun

D8390_TXBUF_SIZE     equ      6
D8390_RXBUF_END      equ      32
D8390_PAGE_SIZE      equ      256

ETH_ALEN         equ      6
ETH_HLEN         equ      14
ETH_ZLEN         equ      60
ETH_FRAME_LEN    equ      1514

FLAG_PIO         equ      0x01
FLAG_16BIT       equ      0x02
ASIC_PIO         equ      0

VENDOR_NONE         equ      0
VENDOR_WD           equ      1
VENDOR_NOVELL       equ      2
VENDOR_3COM         equ      3

NE_ASIC_OFFSET      equ      0x10
NE_RESET            equ      0x0F      ; Used to reset card
NE_DATA             equ      0x00      ; Used to read/write NIC mem

MEM_8192          equ      32
MEM_16384         equ      64
MEM_32768         equ      128

ISA_MAX_ADDR      equ      0x400

uglobal
eth_flags:
                  db   0
eth_vendor:
                  db   0
eth_nic_base:
                  dw   0
eth_asic_base:
                  dw   0
eth_memsize:
                  db   0
eth_rx_start:
                  db   0
eth_tx_start:
                  db   0
eth_bmem:
                  dd   0
eth_rmem:
                  dd   0
romdata:
                  db   0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
endg

iglobal
test_data:
                  db   'NE*000 memory',0
test_buffer:
                  db   '             ',0
endg

uglobal
eth_type:
                  dw   0
pkthdr:
                  db   0,0,0,0  ; status, next, (short) len
pktoff:
                  dw   0
eth_rx_data_ptr:
                  dd   0
eth_tmp_len:
                  dw   0
endg



;***************************************************************************
;   Function
;      eth_pio_read
;
;   Description
;       Read a frame from the ethernet card via Programmed I/O
;      src in ebx
;      cnt in ecx
;       dst in edi
;***************************************************************************
eth_pio_read:
        mov     al, [eth_flags]
        and     al, FLAG_16BIT
        cmp     al, 0
        je      epr_001

        inc     ecx
        and     ecx, 0xFFFFFFFE

epr_001:
        mov     al, D8390_COMMAND_RD2_STA
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_COMMAND
        out     dx, al

        mov     al, cl
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RBCR0
        out     dx, al

        mov     al, ch
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RBCR1
        out     dx, al

        mov     al, bl
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RSAR0
        out     dx, al

        mov     al, bh
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RSAR1
        out     dx, al

        mov     al, D8390_COMMAND_RD0_STA
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_COMMAND
        out     dx, al

        mov     dx, [eth_asic_base]
        add     dx, ASIC_PIO

        mov     al, [eth_flags]
        and     al, FLAG_16BIT
        cmp     al, 0
        je      epr_003

        shr     ecx, 1

epr_002:
   ; 2 bytes at a time
        in      ax, dx
        mov     [edi], ax
        add     edi, 2
        loop    epr_002
        ret

epr_003:
   ; 1 byte at a time
        in      al, dx
        mov     [edi], al
        inc     edi
        loop    epr_003
        ret




;***************************************************************************
;   Function
;      eth_pio_write
;
;   Description
;       writes a frame to the ethernet card via Programmed I/O
;      dst in ebx
;      cnt in ecx
;       src in esi
;***************************************************************************
eth_pio_write:
        mov     al, [eth_flags]
        and     al, FLAG_16BIT
        cmp     al, 0
        je      epw_001

        inc     ecx
        and     ecx, 0xFFFFFFFE

epw_001:
        mov     al, D8390_COMMAND_RD2_STA
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_COMMAND
        out     dx, al

        mov     al, D8390_ISR_RDC
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_ISR
        out     dx, al


        mov     al, cl
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RBCR0
        out     dx, al

        mov     al, ch
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RBCR1
        out     dx, al

        mov     al, bl
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RSAR0
        out     dx, al

        mov     al, bh
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_RSAR1
        out     dx, al

        mov     al, D8390_COMMAND_RD1_STA
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_COMMAND
        out     dx, al

        mov     dx, [eth_asic_base]
        add     dx, ASIC_PIO

        mov     al, [eth_flags]
        and     al, FLAG_16BIT
        cmp     al, 0
        je      epw_003

        shr     ecx, 1

epw_002:
   ; 2 bytes at a time
        mov     ax, [esi]
        add     esi, 2
        out     dx, ax

        loop    epw_002
        jmp     epw_004

epw_003:
   ; 1 byte at a time
        mov     al, [esi]
        inc     esi
        out     dx, al
        loop    epw_003

epw_004:
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_ISR

epw_005:
        in      al, dx
        and     al, D8390_ISR_RDC
        cmp     al, D8390_ISR_RDC
        jne     epw_005

        ret



;***************************************************************************
;   Function
;      rtl8029_reset
;   Description
;      Place the chip (ie, the ethernet card) into a virgin state
;      No inputs
;      All registers destroyed
;
;***************************************************************************
rtl8029_reset:
        mov     bx, [eth_nic_base]

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_PS0_RD2_STP
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_DCR
        mov     al, [eth_flags]
        and     al, FLAG_16BIT
        cmp     al, FLAG_16BIT
        jne     nsr_001

        mov     al, 0x49
        jmp     nsr_002

nsr_001:
        mov     al, 0x48

nsr_002:
        out     dx, al

        xor     al, al

        mov     dx, bx
        add     dx, D8390_P0_RBCR0
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_RBCR1
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_RCR
        mov     al, 0x20
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_TCR
        mov     al, 2
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_TPSR
        mov     al, [eth_tx_start]
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_PSTART
        mov     al, [eth_rx_start]
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_PSTOP
        mov     al, [eth_memsize]
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_BOUND
        mov     al, [eth_memsize]
        dec     al
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_ISR
        mov     al, 0xff
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_IMR
        xor     al, al
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_PS1_RD2_STP
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P1_PAR0
        mov     esi, node_addr
        mov     ecx, ETH_ALEN

nsr_003:
        mov     al, [esi]
        out     dx, al

        inc     esi
        inc     dx
        loop    nsr_003

        mov     dx, bx
        add     dx, D8390_P1_MAR0
        mov     ecx, ETH_ALEN

        mov     al, 0xff

nsr_004:
        out     dx, al
        inc     dx
        loop    nsr_004

        mov     dx, bx
        add     dx, D8390_P1_CURR
        mov     al, [eth_rx_start]
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_PS0_RD2_STA
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_ISR
        mov     al, 0xff
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_TCR
        mov     al, 0
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_RCR
        mov     al, 4
        out     dx, al

        ret



;***************************************************************************
;   Function
;      rtl8029_probe
;   Description
;      Searches for an ethernet card, enables it and clears the rx buffer
;      If a card was found, it enables the ethernet -> TCPIP link
;
;***************************************************************************
rtl8029_probe:
        mov     eax, [io_addr]
        mov     [eth_nic_base], ax  ; The IO address space is 16 bit only

        mov     al, VENDOR_NONE
        mov     [eth_vendor], al

        mov     al, [eth_vendor]
        cmp     al, VENDOR_NONE

        jne     ep_check_have_vendor
        xor     eax, eax
        mov     [eth_bmem], eax

        mov     al, FLAG_PIO
        mov     [eth_flags], al

        mov     ax, [eth_nic_base]
        add     ax, NE_ASIC_OFFSET
        mov     [eth_asic_base], ax

        mov     al, MEM_16384
        mov     [eth_memsize], al

        mov     al, 32
        mov     [eth_tx_start], al

        add     al, D8390_TXBUF_SIZE
        mov     [eth_rx_start], al

        mov     dx, [eth_asic_base]
        add     dx, NE_RESET

        in      al, dx
        out     dx, al

        in      al, 0x84

        mov     bx, [eth_nic_base]

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_RD2_STP
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_RCR
        mov     al, D8390_RCR_MON
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_DCR
        mov     al, D8390_DCR_FT1_LS
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_PSTART
        mov     al, MEM_8192
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_PSTOP
        mov     al, MEM_16384
        out     dx, al

        mov     esi, test_data
        mov     ebx, 8192
        mov     ecx, 14
        call    eth_pio_write

        mov     ebx, 8192
        mov     ecx, 14
        mov     edi, test_buffer
        call    eth_pio_read

        mov     esi, test_buffer
        mov     edi, test_data
        mov     ecx, 13
        cld
        rep cmpsb

        je      ep_set_vendor

        mov     al, [eth_flags]
        or      al, FLAG_16BIT
        mov     [eth_flags], al

        mov     al, MEM_32768
        mov     [eth_memsize], al

        mov     al, 64
        mov     [eth_tx_start], al

        add     al, D8390_TXBUF_SIZE
        mov     [eth_rx_start], al

        mov     bx, [eth_nic_base]

        mov     dx, bx
        add     dx, D8390_P0_DCR
        mov     al, D8390_DCR_WTS_FT1_LS
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_PSTART
        mov     al, MEM_16384
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_PSTOP
        mov     al, MEM_32768
        out     dx, al

        mov     esi, test_data
        mov     ebx, 16384
        mov     ecx, 14
        call    eth_pio_write

        mov     ebx, 16384
        mov     ecx, 14
        mov     edi, test_buffer
        call    eth_pio_read

        mov     esi, test_buffer
        mov     edi, test_data
        mov     ecx, 13
        cld
        rep cmpsb

ep_set_vendor:
   ; this bit is odd - probably left over from my hacking
        mov     ax, [eth_nic_base]
        cmp     ax, 0
        je      rtl8029_exit
        cmp     ax, ISA_MAX_ADDR
        jbe     ep_001
        mov     al, [eth_flags]
        or      al, FLAG_16BIT
        mov     [eth_flags], al

ep_001:
        mov     al, VENDOR_NOVELL
        mov     [eth_vendor], al

        mov     ebx, 0
        mov     ecx, 16
        mov     edi, romdata
        call    eth_pio_read


        mov     ecx, ETH_ALEN
        mov     esi, romdata
        mov     edi, node_addr

        mov     bl, [eth_flags]
        and     bl, FLAG_16BIT

ep_002:
        mov     al, [esi]
        mov     [edi], al

        inc     edi
        inc     esi
        cmp     bl, FLAG_16BIT
        jne     ep_003

        inc     esi

ep_003:
        loop    ep_002

ep_check_have_vendor:
        mov     al, [eth_vendor]
        cmp     al, VENDOR_NONE
        je      rtl8029_exit

        cmp     al, VENDOR_3COM
        je      ep_reset_card

        mov     eax, [eth_bmem]
        mov     [eth_rmem], eax

ep_reset_card:
   ; Reset the card
        call    rtl8029_reset

   ; Indicate that we have successfully reset the card
        mov     eax, [pci_data]
        mov     [eth_status], eax

rtl8029_exit:
        ret



;***************************************************************************
; Function
;    rtl8029_poll
;
; Description
;    Polls the ethernet card for a received packet
;    Received data, if any, ends up in Ether_buffer
;
;***************************************************************************
rtl8029_poll:
        mov     eax, Ether_buffer
        mov     [eth_rx_data_ptr], eax

        mov     bx, [eth_nic_base]

        mov     dx, bx
        add     dx, D8390_P0_RSR
        in      al, dx

        and     al, D8390_RSTAT_PRX
        cmp     al, D8390_RSTAT_PRX
        jne     nsp_exit

        mov     dx, bx
        add     dx, D8390_P0_BOUND
        in      al, dx
        inc     al

        cmp     al, [eth_memsize]
        jb      nsp_001

        mov     al, [eth_rx_start]

nsp_001:
        mov     ch, al

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_PS1
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P1_CURR
        in      al, dx           ; get current page
        mov     cl, al

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_PS0
        out     dx, al

        cmp     cl, [eth_memsize]
        jb      nsp_002

        mov     cl, [eth_rx_start]

nsp_002:
        cmp     cl, ch
        je      nsp_exit

        xor     ax, ax
        mov     ah, ch

        mov     [pktoff], ax

        mov     al, [eth_flags]
        and     al, FLAG_PIO
        cmp     al, FLAG_PIO
        jne     nsp_003

        movzx   ebx, word [pktoff]
        mov     edi, pkthdr
        mov     ecx, 4
        call    eth_pio_read
        jmp     nsp_004

nsp_003:
        mov     edi, [eth_rmem]
        movzx   eax, word [pktoff]
        add     edi, eax
        mov     eax, [edi]
        mov     [pkthdr], eax

nsp_004:
        mov     ax, [pktoff]
        add     ax, 4
        mov     [pktoff], ax

        mov     ax, [pkthdr + 2]
        sub     ax, 4

        mov     [eth_tmp_len], ax

        cmp     ax, ETH_ZLEN
        jb      nsp_exit

        cmp     ax, ETH_FRAME_LEN
        ja      nsp_exit

        mov     al, [pkthdr]
        and     al, D8390_RSTAT_PRX
        cmp     al, D8390_RSTAT_PRX
        jne     nsp_exit

   ; Right, we can now get the data

        mov     ax, [eth_tmp_len]
        mov     [eth_rx_data_len], ax

        xor     ebx, ebx
        mov     bh, [eth_memsize]
        sub     bx, [pktoff]

        cmp     [eth_tmp_len], bx
        jbe     nsp_005

        mov     al, [eth_flags]
        and     al, FLAG_PIO
        cmp     al, FLAG_PIO
        jne     nsp_006

        push    ebx
        mov     ecx, ebx
        xor     ebx, ebx
        mov     bx, [pktoff]
        mov     edi, [eth_rx_data_ptr]
        call    eth_pio_read
        pop     ebx
        jmp     nsp_007

nsp_006:
   ; Not implemented, as we are using PIO mode on this card

nsp_007:
        xor     ax, ax
        mov     ah, [eth_rx_start]
        mov     [pktoff], ax

        mov     eax, [eth_rx_data_ptr]
        add     eax, ebx
        mov     [eth_rx_data_ptr], eax

        mov     ax, [eth_tmp_len]
        sub     ax, bx
        mov     [eth_tmp_len], ax

nsp_005:
        mov     al, [eth_flags]
        and     al, FLAG_PIO
        cmp     al, FLAG_PIO
        jne     nsp_008

        xor     ebx, ebx
        mov     bx, [pktoff]
        xor     ecx, ecx
        mov     cx, [eth_tmp_len]
        mov     edi, [eth_rx_data_ptr]
        call    eth_pio_read
        jmp     nsp_009

nsp_008:
   ; Not implemented, as we are using PIO mode on this card

nsp_009:
        mov     al, [pkthdr+1]
        cmp     al, [eth_rx_start]
        jne     nsp_010

        mov     al, [eth_memsize]

nsp_010:
        mov     dx, [eth_nic_base]
        add     dx, D8390_P0_BOUND
        dec     al
        out     dx, al

nsp_exit:
        ret



;***************************************************************************
;   Function
;      rtl8029_transmit
;
;   Description
;       Transmits a packet of data via the ethernet card
;          Pointer to 48 bit destination address in edi
;         Type of packet in bx
;         size of packet in ecx
;         pointer to packet data in esi
;
;***************************************************************************
rtl8029_transmit:
        mov     [eth_type], bx

        pusha

        mov     esi, edi
        xor     bx, bx
        mov     bh, [eth_tx_start]
        mov     ecx, ETH_ALEN
        call    eth_pio_write

        mov     esi, node_addr
        xor     bx, bx
        mov     bh, [eth_tx_start]
        add     bx, ETH_ALEN
        mov     ecx, ETH_ALEN
        call    eth_pio_write

        mov     esi, eth_type
        xor     bx, bx
        mov     bh, [eth_tx_start]
        add     bx, ETH_ALEN
        add     bx, ETH_ALEN
        mov     ecx, 2
        call    eth_pio_write

        popa

        xor     bx, bx
        mov     bh, [eth_tx_start]
        add     bx, ETH_HLEN
        push    ecx
        call    eth_pio_write
        pop     ecx

        add     ecx, ETH_HLEN
        cmp     ecx, ETH_ZLEN
        jae     nst_001

        mov     ecx, ETH_ZLEN

nst_001:
        push    ecx

        mov     bx, [eth_nic_base]

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_PS0_RD2_STA
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_TPSR
        mov     al, [eth_tx_start]
        out     dx, al

        pop     ecx

        mov     dx, bx
        add     dx, D8390_P0_TBCR0
        mov     al, cl
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_TBCR1
        mov     al, ch
        out     dx, al

        mov     dx, bx
        add     dx, D8390_P0_COMMAND
        mov     al, D8390_COMMAND_PS0_TXP_RD2_STA
        out     dx, al

        ret