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/*****************************************************************************/

/*

 *      baycom.c  -- baycom ser12 and par96 radio modem driver.

 *

 *      Copyright (C) 1996  Thomas Sailer (sailer@ife.ee.ethz.ch)

 *

 *      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; either version 2 of the License, or

 *      (at your option) any later version.

 *

 *      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.

 *

 *  Please note that the GPL allows you to use the driver, NOT the radio.

 *  In order to use the radio, you need a license from the communications

 *  authority of your country.

 *

 *

 *  Supported modems

 *

 *  ser12:  This is a very simple 1200 baud AFSK modem. The modem consists only

 *          of a modulator/demodulator chip, usually a TI TCM3105. The computer

 *          is responsible for regenerating the receiver bit clock, as well as

 *          for handling the HDLC protocol. The modem connects to a serial port,

 *          hence the name. Since the serial port is not used as an async serial

 *          port, the kernel driver for serial ports cannot be used, and this

 *          driver only supports standard serial hardware (8250, 16450, 16550)

 *

 *  par96:  This is a modem for 9600 baud FSK compatible to the G3RUH standard.

 *          The modem does all the filtering and regenerates the receiver clock.

 *          Data is transferred from and to the PC via a shift register.

 *          The shift register is filled with 16 bits and an interrupt is

 *          signalled. The PC then empties the shift register in a burst. This

 *          modem connects to the parallel port, hence the name. The modem

 *          leaves the implementation of the HDLC protocol and the scrambler

 *          polynomial to the PC. This modem is no longer available (at least

 *          from Baycom) and has been replaced by the PICPAR modem (see below).

 *          You may however still build one from the schematics published in

 *          cq-DL :-).

 *

 *  picpar: This is a redesign of the par96 modem by Henning Rech, DF9IC. The

 *          modem is protocol compatible to par96, but uses only three low

 *          power ICs and can therefore be fed from the parallel port and

 *          does not require an additional power supply. It features

 *          built in DCD circuitry. The driver should therefore be configured

 *          for hardware DCD.

 *

 *

 *  Command line options (insmod command line)

 *

 *  mode     driver mode string. Valid choices are ser12 and par96. An

 *           optional * enables software DCD.

 *           2=par96/par97, any other value invalid

 *  iobase   base address of the port; common values are for ser12 0x3f8,

 *           0x2f8, 0x3e8, 0x2e8 and for par96/par97 0x378, 0x278, 0x3bc

 *  irq      interrupt line of the port; common values are for ser12 3,4

 *           and for par96/par97 7

 *

 *

 *  History:

 *   0.1  26.06.96  Adapted from baycom.c and made network driver interface

 *        18.10.96  Changed to new user space access routines (copy_{to,from}_user)

 *   0.3  26.04.96  init code/data tagged

 */

/*****************************************************************************/

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/types.h>

#include <linux/fcntl.h>

#include <linux/interrupt.h>

#include <linux/ioport.h>

#include <linux/in.h>

#include <linux/string.h>

#include <asm/system.h>

#include <asm/bitops.h>

#include <asm/io.h>

#include <linux/delay.h>

#include <linux/errno.h>

#include <linux/netdevice.h>

#include <linux/hdlcdrv.h>

#include <linux/baycom.h>

/* --------------------------------------------------------------------- */

/*

 * currently this module is supposed to support both module styles, i.e.

 * the old one present up to about 2.1.9, and the new one functioning

 * starting with 2.1.21. The reason is I have a kit allowing to compile

 * this module also under 2.0.x which was requested by several people.

 * This will go in 2.2

 */

#include <linux/version.h>

#if LINUX_VERSION_CODE >= 0x20100

#include <asm/uaccess.h>

#else

#include <asm/segment.h>

#include <linux/mm.h>

#undef put_user

#undef get_user

#define put_user(x,ptr) ({ __put_user((unsigned long)(x),(ptr),sizeof(*(ptr))); 0; })

#define get_user(x,ptr) ({ x = ((__typeof__(*(ptr)))__get_user((ptr),sizeof(*(ptr)))); 0; })

extern inline int copy_from_user(void *to, const void *from, unsigned long n)

{

        int i = verify_area(VERIFY_READ, from, n);

        if (i)

                return i;

        memcpy_fromfs(to, from, n);

        return 0;

}

extern inline int copy_to_user(void *to, const void *from, unsigned long n)

{

        int i = verify_area(VERIFY_WRITE, to, n);

        if (i)

                return i;

        memcpy_tofs(to, from, n);

        return 0;

}

#endif

#if LINUX_VERSION_CODE >= 0x20123

#include <linux/init.h>

#else

#define __init

#define __initdata

#define __initfunc(x) x

#endif

/* --------------------------------------------------------------------- */

#define BAYCOM_DEBUG

/*

 * modem options; bit mask

 */

#define BAYCOM_OPTIONS_SOFTDCD  1

/* --------------------------------------------------------------------- */

static const char bc_drvname[] = "baycom";

static const char bc_drvinfo[] = KERN_INFO "baycom: (C) 1996 Thomas Sailer, HB9JNX/AE4WA\n"

KERN_INFO "baycom: version 0.3 compiled " __TIME__ " " __DATE__ "\n";

/* --------------------------------------------------------------------- */

#define NR_PORTS 4

static struct device baycom_device[NR_PORTS];

static struct {

        char *mode;

        int iobase, irq;

} baycom_ports[NR_PORTS] = { { NULL, 0, 0 }, };

/* --------------------------------------------------------------------- */

#define RBR(iobase) (iobase+0)

#define THR(iobase) (iobase+0)

#define IER(iobase) (iobase+1)

#define IIR(iobase) (iobase+2)

#define FCR(iobase) (iobase+2)

#define LCR(iobase) (iobase+3)

#define MCR(iobase) (iobase+4)

#define LSR(iobase) (iobase+5)

#define MSR(iobase) (iobase+6)

#define SCR(iobase) (iobase+7)

#define DLL(iobase) (iobase+0)

#define DLM(iobase) (iobase+1)

#define SER12_EXTENT 8

#define LPT_DATA(iobase)    (iobase+0)

#define LPT_STATUS(iobase)  (iobase+1)

#define LPT_CONTROL(iobase) (iobase+2)

#define LPT_IRQ_ENABLE      0x10

#define PAR96_BURSTBITS 16

#define PAR96_BURST     4

#define PAR96_PTT       2

#define PAR96_TXBIT     1

#define PAR96_ACK       0x40

#define PAR96_RXBIT     0x20

#define PAR96_DCD       0x10

#define PAR97_POWER     0xf8

#define PAR96_EXTENT 3

/* ---------------------------------------------------------------------- */

/*

 * Information that need to be kept for each board.

 */

struct baycom_state {

        struct hdlcdrv_state hdrv;

        unsigned int options;

        struct modem_state {

                short arb_divider;

                unsigned char flags;

                unsigned int shreg;

                struct modem_state_ser12 {

                        unsigned char last_sample;

                        unsigned char interm_sample;

                        unsigned int bit_pll;

                        unsigned int dcd_shreg;

                        int dcd_sum0, dcd_sum1, dcd_sum2;

                        unsigned int dcd_time;

                        unsigned char last_rxbit;

                        unsigned char tx_bit;

                } ser12;

                struct modem_state_par96 {

                        int dcd_count;

                        unsigned int dcd_shreg;

                        unsigned long descram;

                        unsigned long scram;

                } par96;

        } modem;

#ifdef BAYCOM_DEBUG

        struct debug_vals {

                unsigned long last_jiffies;

                unsigned cur_intcnt;

                unsigned last_intcnt;

                int cur_pllcorr;

                int last_pllcorr;

        } debug_vals;

#endif /* BAYCOM_DEBUG */

};

/* --------------------------------------------------------------------- */

#define min(a, b) (((a) < (b)) ? (a) : (b))

#define max(a, b) (((a) > (b)) ? (a) : (b))

/* --------------------------------------------------------------------- */

static void inline baycom_int_freq(struct baycom_state *bc)

{

#ifdef BAYCOM_DEBUG

        unsigned long cur_jiffies = jiffies;

        /*

         * measure the interrupt frequency

         */

        bc->debug_vals.cur_intcnt++;

        if ((cur_jiffies - bc->debug_vals.last_jiffies) >= HZ) {

                bc->debug_vals.last_jiffies = cur_jiffies;

                bc->debug_vals.last_intcnt = bc->debug_vals.cur_intcnt;

                bc->debug_vals.cur_intcnt = 0;

                bc->debug_vals.last_pllcorr = bc->debug_vals.cur_pllcorr;

                bc->debug_vals.cur_pllcorr = 0;

        }

#endif /* BAYCOM_DEBUG */

}

/* --------------------------------------------------------------------- */

/*

 * ===================== SER12 specific routines =========================

 */

static void inline ser12_set_divisor(struct device *dev,

                                     unsigned char divisor)

{

        outb(0x81, LCR(dev->base_addr));        /* DLAB = 1 */

        outb(divisor, DLL(dev->base_addr));

        outb(0, DLM(dev->base_addr));

        outb(0x01, LCR(dev->base_addr));        /* word length = 6 */

        /*

         * make sure the next interrupt is generated;

         * 0 must be used to power the modem; the modem draws its

         * power from the TxD line

         */

        outb(0x00, THR(dev->base_addr));

        /*

         * it is important not to set the divider while transmitting;

         * this reportedly makes some UARTs generating interrupts

         * in the hundredthousands per second region

         * Reported by: Ignacio.Arenaza@studi.epfl.ch (Ignacio Arenaza Nuno)

         */

}

/* --------------------------------------------------------------------- */

/*

 * must call the TX arbitrator every 10ms

 */

#define SER12_ARB_DIVIDER(bc) ((bc->options & BAYCOM_OPTIONS_SOFTDCD) ? \

                               36 : 24)

#define SER12_DCD_INTERVAL(bc) ((bc->options & BAYCOM_OPTIONS_SOFTDCD) ? \

                                240 : 12)

static inline void ser12_tx(struct device *dev, struct baycom_state *bc)

{

        /* one interrupt per channel bit */

        ser12_set_divisor(dev, 12);

        /*

         * first output the last bit (!) then call HDLC transmitter,

         * since this may take quite long

         */

        outb(0x0e | (!!bc->modem.ser12.tx_bit), MCR(dev->base_addr));

        if (bc->modem.shreg <= 1)

                bc->modem.shreg = 0x10000 | hdlcdrv_getbits(&bc->hdrv);

        bc->modem.ser12.tx_bit = !(bc->modem.ser12.tx_bit ^

                                   (bc->modem.shreg & 1));

        bc->modem.shreg >>= 1;

}

/* --------------------------------------------------------------------- */

static inline void ser12_rx(struct device *dev, struct baycom_state *bc)

{

        unsigned char cur_s;

        /*

         * do demodulator

         */

        cur_s = inb(MSR(dev->base_addr)) & 0x10;        /* the CTS line */

        hdlcdrv_channelbit(&bc->hdrv, cur_s);

        bc->modem.ser12.dcd_shreg = (bc->modem.ser12.dcd_shreg << 1) |

                (cur_s != bc->modem.ser12.last_sample);

        bc->modem.ser12.last_sample = cur_s;

        if(bc->modem.ser12.dcd_shreg & 1) {

                if (bc->options & BAYCOM_OPTIONS_SOFTDCD) {

                        unsigned int dcdspos, dcdsneg;

                        dcdspos = dcdsneg = 0;

                        dcdspos += ((bc->modem.ser12.dcd_shreg >> 1) & 1);

                        if (!(bc->modem.ser12.dcd_shreg & 0x7ffffffe))

                                dcdspos += 2;

                        dcdsneg += ((bc->modem.ser12.dcd_shreg >> 2) & 1);

                        dcdsneg += ((bc->modem.ser12.dcd_shreg >> 3) & 1);

                        dcdsneg += ((bc->modem.ser12.dcd_shreg >> 4) & 1);

                        bc->modem.ser12.dcd_sum0 += 16*dcdspos - dcdsneg;

                } else

                        bc->modem.ser12.dcd_sum0--;

        }

        if(!bc->modem.ser12.dcd_time) {

                hdlcdrv_setdcd(&bc->hdrv, (bc->modem.ser12.dcd_sum0 +

                                           bc->modem.ser12.dcd_sum1 +

                                           bc->modem.ser12.dcd_sum2) < 0);

                bc->modem.ser12.dcd_sum2 = bc->modem.ser12.dcd_sum1;

                bc->modem.ser12.dcd_sum1 = bc->modem.ser12.dcd_sum0;

                /* offset to ensure DCD off on silent input */

                bc->modem.ser12.dcd_sum0 = 2;

                bc->modem.ser12.dcd_time = SER12_DCD_INTERVAL(bc);

        }

        bc->modem.ser12.dcd_time--;

        if (bc->options & BAYCOM_OPTIONS_SOFTDCD) {

                /*

                 * PLL code for the improved software DCD algorithm

                 */

                if (bc->modem.ser12.interm_sample) {

                        /*

                         * intermediate sample; set timing correction to normal

                         */

                        ser12_set_divisor(dev, 4);

                } else {

                        /*

                         * do PLL correction and call HDLC receiver

                         */

                        switch (bc->modem.ser12.dcd_shreg & 7) {

                        case 1: /* transition too late */

                                ser12_set_divisor(dev, 5);

#ifdef BAYCOM_DEBUG

                                bc->debug_vals.cur_pllcorr++;

#endif /* BAYCOM_DEBUG */

                                break;

                        case 4: /* transition too early */

                                ser12_set_divisor(dev, 3);

#ifdef BAYCOM_DEBUG

                                bc->debug_vals.cur_pllcorr--;

#endif /* BAYCOM_DEBUG */

                                break;

                        default:

                                ser12_set_divisor(dev, 4);

                                break;

                        }

                        bc->modem.shreg >>= 1;

                        if (bc->modem.ser12.last_sample ==

                            bc->modem.ser12.last_rxbit)

                                bc->modem.shreg |= 0x10000;

                        bc->modem.ser12.last_rxbit =

                                bc->modem.ser12.last_sample;

                }

                if (++bc->modem.ser12.interm_sample >= 3)

                        bc->modem.ser12.interm_sample = 0;

                /*

                 * DCD stuff

                 */

                if (bc->modem.ser12.dcd_shreg & 1) {

                        unsigned int dcdspos, dcdsneg;

                        dcdspos = dcdsneg = 0;

                        dcdspos += ((bc->modem.ser12.dcd_shreg >> 1) & 1);

                        dcdspos += (!(bc->modem.ser12.dcd_shreg & 0x7ffffffe))

                                << 1;

                        dcdsneg += ((bc->modem.ser12.dcd_shreg >> 2) & 1);

                        dcdsneg += ((bc->modem.ser12.dcd_shreg >> 3) & 1);

                        dcdsneg += ((bc->modem.ser12.dcd_shreg >> 4) & 1);

                        bc->modem.ser12.dcd_sum0 += 16*dcdspos - dcdsneg;

                }

        } else {

                /*

                 * PLL algorithm for the hardware squelch DCD algorithm

                 */

                if (bc->modem.ser12.interm_sample) {

                        /*

                         * intermediate sample; set timing correction to normal

                         */

                        ser12_set_divisor(dev, 6);

                } else {

                        /*

                         * do PLL correction and call HDLC receiver

                         */

                        switch (bc->modem.ser12.dcd_shreg & 3) {

                        case 1: /* transition too late */

                                ser12_set_divisor(dev, 7);

#ifdef BAYCOM_DEBUG

                                bc->debug_vals.cur_pllcorr++;

#endif /* BAYCOM_DEBUG */

                                break;

                        case 2: /* transition too early */

                                ser12_set_divisor(dev, 5);

#ifdef BAYCOM_DEBUG

                                bc->debug_vals.cur_pllcorr--;

#endif /* BAYCOM_DEBUG */

                                break;

                        default:

                                ser12_set_divisor(dev, 6);

                                break;

                        }

                        bc->modem.shreg >>= 1;

                        if (bc->modem.ser12.last_sample ==

                            bc->modem.ser12.last_rxbit)

                                bc->modem.shreg |= 0x10000;

                        bc->modem.ser12.last_rxbit =

                                bc->modem.ser12.last_sample;

                }

                bc->modem.ser12.interm_sample = !bc->modem.ser12.interm_sample;

                /*

                 * DCD stuff

                 */

                bc->modem.ser12.dcd_sum0 -= (bc->modem.ser12.dcd_shreg & 1);

        }

        outb(0x0d, MCR(dev->base_addr));                /* transmitter off */

        if (bc->modem.shreg & 1) {

                hdlcdrv_putbits(&bc->hdrv, bc->modem.shreg >> 1);

                bc->modem.shreg = 0x10000;

        }

        if(!bc->modem.ser12.dcd_time) {

                hdlcdrv_setdcd(&bc->hdrv, (bc->modem.ser12.dcd_sum0 +

                                           bc->modem.ser12.dcd_sum1 +

                                           bc->modem.ser12.dcd_sum2) < 0);

                bc->modem.ser12.dcd_sum2 = bc->modem.ser12.dcd_sum1;

                bc->modem.ser12.dcd_sum1 = bc->modem.ser12.dcd_sum0;

                /* offset to ensure DCD off on silent input */

                bc->modem.ser12.dcd_sum0 = 2;

                bc->modem.ser12.dcd_time = SER12_DCD_INTERVAL(bc);

        }

        bc->modem.ser12.dcd_time--;

}

/* --------------------------------------------------------------------- */

static void ser12_interrupt(int irq, void *dev_id, struct pt_regs *regs)

{

        struct device *dev = (struct device *)dev_id;

        struct baycom_state *bc = (struct baycom_state *)dev->priv;

        if (!dev || !bc || bc->hdrv.magic != HDLCDRV_MAGIC)

                return;

        baycom_int_freq(bc);

        /*

         * check if transmitter active

         */

        if (hdlcdrv_ptt(&bc->hdrv))

                ser12_tx(dev, bc);

        else {

                ser12_rx(dev, bc);

                if (--bc->modem.arb_divider <= 0) {

                        bc->modem.arb_divider = SER12_ARB_DIVIDER(bc);

                        sti();

                        hdlcdrv_arbitrate(dev, &bc->hdrv);

                }

        }

        sti();

        hdlcdrv_transmitter(dev, &bc->hdrv);

        hdlcdrv_receiver(dev, &bc->hdrv);

}

/* --------------------------------------------------------------------- */

enum uart { c_uart_unknown, c_uart_8250,

        c_uart_16450, c_uart_16550, c_uart_16550A};

static const char *uart_str[] =

        { "unknown", "8250", "16450", "16550", "16550A" };

static enum uart ser12_check_uart(unsigned int iobase)

{

        unsigned char b1,b2,b3;

        enum uart u;

        enum uart uart_tab[] =

                { c_uart_16450, c_uart_unknown, c_uart_16550, c_uart_16550A };

        b1 = inb(MCR(iobase));

        outb(b1 | 0x10, MCR(iobase));   /* loopback mode */

        b2 = inb(MSR(iobase));

        outb(0x1a, MCR(iobase));

        b3 = inb(MSR(iobase)) & 0xf0;

        outb(b1, MCR(iobase));                  /* restore old values */

        outb(b2, MSR(iobase));

        if (b3 != 0x90)

                return c_uart_unknown;

        inb(RBR(iobase));

        inb(RBR(iobase));

        outb(0x01, FCR(iobase));                /* enable FIFOs */

        u = uart_tab[(inb(IIR(iobase)) >> 6) & 3];

        if (u == c_uart_16450) {

                outb(0x5a, SCR(iobase));

                b1 = inb(SCR(iobase));

                outb(0xa5, SCR(iobase));

                b2 = inb(SCR(iobase));

                if ((b1 != 0x5a) || (b2 != 0xa5))

                        u = c_uart_8250;

        }

        return u;

}

/* --------------------------------------------------------------------- */

static int ser12_open(struct device *dev)

{

        struct baycom_state *bc = (struct baycom_state *)dev->priv;

        enum uart u;

        if (!dev || !bc)

                return -ENXIO;

        if (!dev->base_addr || dev->base_addr > 0x1000-SER12_EXTENT ||

            dev->irq < 2 || dev->irq > 15)

                return -ENXIO;

        if (check_region(dev->base_addr, SER12_EXTENT))

                return -EACCES;

        memset(&bc->modem, 0, sizeof(bc->modem));

        bc->hdrv.par.bitrate = 1200;

        if ((u = ser12_check_uart(dev->base_addr)) == c_uart_unknown)

                return -EIO;

        outb(0, FCR(dev->base_addr));  /* disable FIFOs */

        outb(0x0d, MCR(dev->base_addr));

        outb(0x0d, MCR(dev->base_addr));

        outb(0, IER(dev->base_addr));

        if (request_irq(dev->irq, ser12_interrupt, SA_INTERRUPT,

                        "baycom_ser12", dev))

                return -EBUSY;

        request_region(dev->base_addr, SER12_EXTENT, "baycom_ser12");

        /*

         * enable transmitter empty interrupt

         */

        outb(2, IER(dev->base_addr));

        /*

         * set the SIO to 6 Bits/character and 19200 or 28800 baud, so that

         * we get exactly (hopefully) 2 or 3 interrupts per radio symbol,

         * depending on the usage of the software DCD routine

         */

        ser12_set_divisor(dev, (bc->options & BAYCOM_OPTIONS_SOFTDCD) ? 4 : 6);

        printk(KERN_INFO "%s: ser12 at iobase 0x%lx irq %u options "

               "0x%x uart %s\n", bc_drvname, dev->base_addr, dev->irq,

               bc->options, uart_str[u]);

        MOD_INC_USE_COUNT;

        return 0;

}

/* --------------------------------------------------------------------- */

static int ser12_close(struct device *dev)

{

        struct baycom_state *bc = (struct baycom_state *)dev->priv;

        if (!dev || !bc)

                return -EINVAL;

        /*

         * disable interrupts

         */

        outb(0, IER(dev->base_addr));

        outb(1, MCR(dev->base_addr));

        free_irq(dev->irq, dev);

        release_region(dev->base_addr, SER12_EXTENT);

        printk(KERN_INFO "%s: close ser12 at iobase 0x%lx irq %u\n",

               bc_drvname, dev->base_addr, dev->irq);

        MOD_DEC_USE_COUNT;

        return 0;

}

/* --------------------------------------------------------------------- */

/*

 * ===================== PAR96 specific routines =========================

 */

#define PAR96_DESCRAM_TAP1 0x20000

#define PAR96_DESCRAM_TAP2 0x01000

#define PAR96_DESCRAM_TAP3 0x00001

#define PAR96_DESCRAM_TAPSH1 17

#define PAR96_DESCRAM_TAPSH2 12

#define PAR96_DESCRAM_TAPSH3 0

#define PAR96_SCRAM_TAP1 0x20000 /* X^17 */

#define PAR96_SCRAM_TAPN 0x00021 /* X^0+X^5 */

/* --------------------------------------------------------------------- */

static inline void par96_tx(struct device *dev, struct baycom_state *bc)

{

        int i;

        unsigned int data = hdlcdrv_getbits(&bc->hdrv);

        for(i = 0; i < PAR96_BURSTBITS; i++, data >>= 1) {

                unsigned char val = PAR97_POWER;

                bc->modem.par96.scram = ((bc->modem.par96.scram << 1) |

                                         (bc->modem.par96.scram & 1));

                if (!(data & 1))

                        bc->modem.par96.scram ^= 1;

                if (bc->modem.par96.scram & (PAR96_SCRAM_TAP1 << 1))

                        bc->modem.par96.scram ^=

                                (PAR96_SCRAM_TAPN << 1);

                if (bc->modem.par96.scram & (PAR96_SCRAM_TAP1 << 2))

                        val |= PAR96_TXBIT;

                outb(val, LPT_DATA(dev->base_addr));

                outb(val | PAR96_BURST, LPT_DATA(dev->base_addr));

        }

}

/* --------------------------------------------------------------------- */

static inline void par96_rx(struct device *dev, struct baycom_state *bc)

{

        int i;

        unsigned int data, mask, mask2, descx;

        /*

         * do receiver; differential decode and descramble on the fly

         */

        for(data = i = 0; i < PAR96_BURSTBITS; i++) {

                bc->modem.par96.descram = (bc->modem.par96.descram << 1);

                if (inb(LPT_STATUS(dev->base_addr)) & PAR96_RXBIT)

                        bc->modem.par96.descram |= 1;

                descx = bc->modem.par96.descram ^

                        (bc->modem.par96.descram >> 1);

                /* now the diff decoded data is inverted in descram */

                outb(PAR97_POWER | PAR96_PTT, LPT_DATA(dev->base_addr));

                descx ^= ((descx >> PAR96_DESCRAM_TAPSH1) ^