src/include/z8530reg.h

/*  GXemul: $Id: z8530reg.h,v 1.1 2005/12/02 01:46:31 debug Exp $  */
/*      $NetBSD: z8530reg.h,v 1.11 2003/11/02 11:07:46 wiz Exp $ */

#ifndef Z8530REG_H
#define Z8530REG_H

/*
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * All advertising materials mentioning features or use of this software
 * must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Lawrence Berkeley Laboratory.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)zsreg.h     8.1 (Berkeley) 6/11/93
 */

/*
 * Zilog SCC registers, as implemented on the Sun-4c.
 *
 * Each Z8530 implements two channels (called `a' and `b').
 *
 * The damnable chip was designed to fit on Z80 I/O ports, and thus
 * has everything multiplexed out the wazoo.  We have to select
 * a register, then read or write the register, and so on.  Worse,
 * the parameter bits are scattered all over the register space.
 * This thing is full of `miscellaneous' control registers.
 *
 * Worse yet, the registers have incompatible functions on read
 * and write operations.  We describe the registers below according
 * to whether they are `read registers' (RR) or `write registers' (WR).
 * As if this were not enough, some of the channel B status bits show
 * up in channel A, and vice versa.  The blasted thing shares write
 * registers 2 and 9 across both channels, and reads registers 2 and 3
 * differently for the two channels.  We can, however, ignore this much
 * of the time.
 *
 * This file also includes flags for the Z85C30 and Z85230 enhanced scc.
 * The CMOS 8530 includes extra SDLC functionality, and is used in a
 * number of Macs (often in the Z85C80, an 85C30 combined w/ a SCSI
 * controller). -wrs
 *
 * Some of the names in this files were chosen to make the hsis driver
 * work unchanged (which means that they will match some in SunOS).
 *
 * `S.C.' stands for Special Condition, which is any of these:
 *      receiver overrun        (aka silo overflow)
 *      framing error           (missing stop bit, etc)
 *      end of frame            (in synchronous modes)
 *      parity error            (when `parity error is S.C.' is set)
 *
 * Registers with only a single `numeric value' get a name.
 * Other registers hold bits and are only numbered; the bit
 * definitions imply the register number (see below).
 *
 * We never use the receive and transmit data registers as
 * indirects (choosing instead the zc_data register), so they
 * are not defined here.
 */
#define ZSRR_IVEC       2       /* interrupt vector (channel 0) */
#define ZSRR_IPEND      3       /* interrupt pending (ch. 0 only) */
#define ZSRR_TXSYNC     6       /* sync transmit char (monosync mode) */
#define ZSRR_RXSYNC     7       /* sync receive char (monosync mode) */
#define ZSRR_SYNCLO     6       /* sync low byte (bisync mode) */
#define ZSRR_SYNCHI     7       /* sync high byte (bisync mode) */
#define ZSRR_SDLC_ADDR  6       /* SDLC address (SDLC mode) */
#define ZSRR_SDLC_FLAG  7       /* SDLC flag 0x7E (SDLC mode) */
#define ZSRR_BAUDLO     12      /* baud rate generator (low half) */
#define ZSRR_BAUDHI     13      /* baud rate generator (high half) */
#define ZSRR_ENHANCED   14      /* read address of WR7' - yes, it's not 7!*/

#define ZSWR_IVEC       2       /* interrupt vector (shared) */
#define ZSWR_TXSYNC     6       /* sync transmit char (monosync mode) */
#define ZSWR_RXSYNC     7       /* sync receive char (monosync mode) */
#define ZSWR_SYNCLO     6       /* sync low byte (bisync mode) */
#define ZSWR_SYNCHI     7       /* sync high byte (bisync mode) */
#define ZSWR_SDLC_ADDR  6       /* SDLC address (SDLC mode) */
#define ZSWR_SDLC_FLAG  7       /* SDLC flag 0x7E (SDLC mode) */
#define ZSWR_BAUDLO     12      /* baud rate generator (low half) */
#define ZSWR_BAUDHI     13      /* baud rate generator (high half) */
#define ZSWR_ENHANCED   7       /* write address of WR7' */

/*
 * Registers 0 through 7 may be written with any one of the 8 command
 * modifiers, and/or any one of the 4 reset modifiers, defined below.
 * To write registers 8 through 15, however, the command modifier must
 * always be `point high'.  Rather than track this bizzareness all over
 * the driver, we try to avoid using any modifiers, ever (but they are
 * defined here if you want them).
 */
#define ZSM_RESET_TXUEOM        0xc0    /* reset xmit underrun / eom latch */
#define ZSM_RESET_TXCRC         0x80    /* reset xmit crc generator */
#define ZSM_RESET_RXCRC         0x40    /* reset recv crc checker */
#define ZSM_NULL                0x00    /* nothing special */

#define ZSM_RESET_IUS           0x38    /* reset interrupt under service */
#define ZSM_RESET_ERR           0x30    /* reset error cond */
#define ZSM_RESET_TXINT         0x28    /* reset xmit interrupt pending */
#define ZSM_EI_NEXTRXC          0x20    /* enable int. on next rcvd char */
#define ZSM_SEND_ABORT          0x18    /* send abort (SDLC) */
#define ZSM_RESET_STINT         0x10    /* reset external/status interrupt */
#define ZSM_POINTHIGH           0x08    /* `point high' (use r8-r15) */
#define ZSM_NULL                0x00    /* nothing special */

/*
 * Commands for Write Register 0 (`Command Register').
 * These are just the command modifiers or'ed with register number 0
 * (which of course equals the command modifier).
 */
#define ZSWR0_RESET_EOM         ZSM_RESET_TXUEOM
#define ZSWR0_RESET_TXCRC       ZSM_RESET_TXCRC
#define ZSWR0_RESET_RXCRC       ZSM_RESET_RXCRC
#define ZSWR0_CLR_INTR          ZSM_RESET_IUS
#define ZSWR0_RESET_ERRORS      ZSM_RESET_ERR
#define ZSWR0_EI_NEXTRXC        ZSM_EI_NEXTRXC
#define ZSWR0_SEND_ABORT        ZSM_SEND_ABORT
#define ZSWR0_RESET_STATUS      ZSM_RESET_STINT
#define ZSWR0_RESET_TXINT       ZSM_RESET_TXINT

/*
 * Bits in Write Register 1 (`Transmit/Receive Interrupt and Data
 * Transfer Mode Definition').  Note that bits 3 and 4 are taken together
 * as a single unit, and bits 5 and 6 are useful only if bit 7 is set.
 */
#define ZSWR1_REQ_WAIT          0x80    /* WAIT*-REQ* pin gives WAIT* */
#define ZSWR1_REQ_REQ           0xc0    /* WAIT*-REQ* pin gives REQ* */
#define ZSWR1_REQ_TX            0x00    /* WAIT*-REQ* pin follows xmit buf */
#define ZSWR1_REQ_RX            0x20    /* WAIT*-REQ* pin follows recv buf */

#define ZSWR1_RIE_NONE          0x00    /* disable rxint entirely */
#define ZSWR1_RIE_FIRST         0x08    /* rxint on first char & on S.C. */
#define ZSWR1_RIE               0x10    /* rxint per char & on S.C. */
#define ZSWR1_RIE_SPECIAL_ONLY  0x18    /* rxint on S.C. only */

#define ZSWR1_PE_SC             0x04    /* parity error is special condition */
#define ZSWR1_TIE               0x02    /* transmit interrupt enable */
#define ZSWR1_SIE               0x01    /* external/status interrupt enable */

#define ZSWR1_IMASK     0x1F    /* mask of all itr. enable bits. */

/* HSIS compat */
#define ZSWR1_REQ_ENABLE        (ZSWR1_REQ_WAIT | ZSWR1_REQ_TX)

/*
 * Bits in Write Register 3 (`Receive Parameters and Control').
 * Bits 7 and 6 are taken as a unit.  Note that the receive bits
 * per character ordering is insane.
 *
 * Here `hardware flow control' means CTS enables the transmitter
 * and DCD enables the receiver.  The latter is neither interesting
 * nor useful, and gets in our way, making it almost unusable.
 */
#define ZSWR3_RX_5              0x00    /* receive 5 bits per char */
#define ZSWR3_RX_7              0x40    /* receive 7 bits per char */
#define ZSWR3_RX_6              0x80    /* receive 6 bits per char */
#define ZSWR3_RX_8              0xc0    /* receive 8 bits per char */
#define ZSWR3_RXSIZE            0xc0    /* receive char size mask */

#define ZSWR3_HFC               0x20    /* hardware flow control */
#define ZSWR3_HUNT              0x10    /* enter hunt mode */
#define ZSWR3_RXCRC_ENABLE      0x08    /* enable recv crc calculation */
#define ZSWR3_ADDR_SEARCH_MODE  0x04    /* address search mode (SDLC only) */
#define ZSWR3_SDLC_SHORT_ADDR   0x02    /* short address mode (SDLC only) */
#define ZSWR3_SYNC_LOAD_INH     0x02    /* sync character load inhibit */
#define ZSWR3_RX_ENABLE         0x01    /* receiver enable */

/*
 * Bits in Write Register 4 (`Transmit/Receive Miscellaneous Parameters
 * and Modes').  Bits 7&6, 5&4, and 3&2 are taken as units.
 */
#define ZSWR4_CLK_X1            0x00    /* clock divisor = 1 */
#define ZSWR4_CLK_X16           0x40    /* clock divisor = 16 */
#define ZSWR4_CLK_X32           0x80    /* clock divisor = 32 */
#define ZSWR4_CLK_X64           0xc0    /* clock divisor = 64 */
#define ZSWR4_CLK_MASK          0xc0    /* clock divisor mask */

#define ZSWR4_MONOSYNC          0x00    /* 8 bit sync char (sync only) */
#define ZSWR4_BISYNC            0x10    /* 16 bit sync char (sync only) */
#define ZSWR4_SDLC              0x20    /* SDLC mode */
#define ZSWR4_EXTSYNC           0x30    /* external sync mode */
#define ZSWR4_SYNC_MASK         0x30    /* sync mode bit mask */

#define ZSWR4_SYNCMODE          0x00    /* no stop bit (sync mode only) */
#define ZSWR4_ONESB             0x04    /* 1 stop bit */
#define ZSWR4_1P5SB             0x08    /* 1.5 stop bits (clk cannot be 1x) */
#define ZSWR4_TWOSB             0x0c    /* 2 stop bits */
#define ZSWR4_SBMASK            0x0c    /* mask of all stop bits */

#define ZSWR4_EVENP             0x02    /* check for even parity */
#define ZSWR4_PARENB            0x01    /* enable parity checking */
#define ZSWR4_PARMASK           0x03    /* mask of all parity bits */

/*
 * Bits in Write Register 5 (`Transmit Parameter and Controls').
 * Bits 6 and 5 are taken as a unit; the ordering is, as with RX
 * bits per char, not sensible.
 */
#define ZSWR5_DTR               0x80    /* assert (set to -12V) DTR */

#define ZSWR5_TX_5              0x00    /* transmit 5 or fewer bits */
#define ZSWR5_TX_7              0x20    /* transmit 7 bits */
#define ZSWR5_TX_6              0x40    /* transmit 6 bits */
#define ZSWR5_TX_8              0x60    /* transmit 8 bits */
#define ZSWR5_TXSIZE            0x60    /* transmit char size mask */

#define ZSWR5_BREAK             0x10    /* send break (continuous 0s) */
#define ZSWR5_TX_ENABLE         0x08    /* enable transmitter */
#define ZSWR5_CRC16             0x04    /* use CRC16 (off => use SDLC) */
#define ZSWR5_RTS               0x02    /* assert RTS */
#define ZSWR5_TXCRC_ENABLE      0x01    /* enable xmit crc calculation */

#ifdef not_done_here
/*
 * Bits in Write Register 7 when the chip is in SDLC mode.
 */
#define ZSWR7_SDLCFLAG          0x7e    /* this value makes SDLC mode work */
#endif

/*
 * Bits in Write Register 7' (ZSWR_ENHANCED above). This register is
 * only available on the 85230. Dispite the fact it contains flags
 * and not a single value, the register was named as it is read
 * via RR14. Weird.
 */
                        /*      0x80    unused */
#define ZSWR7P_EXTEND_READ      0x40    /* modify read map; make most regs readable */
#define ZSWR7P_TX_FIFO          0x20    /* change level for Tx FIFO empty int */
#define ZSWR7P_DTR_TIME         0x10    /* modifies deact. speed of /DTR//REQ */
#define ZSWR7P_RX_FIFO          0x08    /* Rx FIFO int on 1/2 full? */
#define ZSWR7P_RTS_DEACT        0x04    /* automatically deassert RTS */
#define ZSWR7P_AUTO_EOM_RESET   0x02    /* automatically reset EMO/Tx Underrun */
#define ZSWR7P_AUTO_TX_FLAG     0x01    /* Auto send SDLC flag at transmit start */

/*
 * Bits in Write Register 9 (`Master Interrupt Control').  Bits 7 & 6
 * are taken as a unit and indicate the type of reset; 00 means no reset
 * (and is not defined here).
 */
#define ZSWR9_HARD_RESET        0xc0    /* force hardware reset */
#define ZSWR9_A_RESET           0x80    /* reset channel A (0) */
#define ZSWR9_B_RESET           0x40    /* reset channel B (1) */
#define ZSWR9_SOFT_INTAC        0x20    /* Not in NMOS version */

#define ZSWR9_STATUS_HIGH       0x10    /* status in high bits of intr vec */
#define ZSWR9_MASTER_IE         0x08    /* master interrupt enable */
#define ZSWR9_DLC               0x04    /* disable lower chain */
#define ZSWR9_NO_VECTOR         0x02    /* no vector */
#define ZSWR9_VECTOR_INCL_STAT  0x01    /* vector includes status */

/*
 * Bits in Write Register 10 (`Miscellaneous Transmitter/Receiver Control
 * Bits').  Bits 6 & 5 are taken as a unit, and some of the bits are
 * meaningful only in certain modes.  Bleah.
 */
#define ZSWR10_PRESET_ONES      0x80    /* preset CRC to all 1 (else all 0) */

#define ZSWR10_NRZ              0x00    /* NRZ encoding */
#define ZSWR10_NRZI             0x20    /* NRZI encoding */
#define ZSWR10_FM1              0x40    /* FM1 encoding */
#define ZSWR10_FM0              0x60    /* FM0 encoding */

#define ZSWR10_GA_ON_POLL       0x10    /* go active on poll (loop mode) */
#define ZSWR10_MARK_IDLE        0x08    /* all 1s (vs flag) when idle (SDLC) */
#define ZSWR10_ABORT_ON_UNDERRUN 0x4    /* abort on xmit underrun (SDLC) */
#define ZSWR10_LOOP_MODE        0x02    /* loop mode (SDLC) */
#define ZSWR10_6_BIT_SYNC       0x01    /* 6 bits per sync char (sync modes) */

/*
 * Bits in Write Register 11 (`Clock Mode Control').  Bits 6&5, 4&3, and
 * 1&0 are taken as units.  Various bits depend on other bits in complex
 * ways; see the Zilog manual.
 */
#define ZSWR11_XTAL             0x80    /* have xtal between RTxC* and SYNC* */
                                        /* (else have TTL oscil. on RTxC*) */
#define ZSWR11_RXCLK_RTXC       0x00    /* recv clock taken from RTxC* pin */
#define ZSWR11_RXCLK_TRXC       0x20    /* recv clock taken from TRxC* pin */
#define ZSWR11_RXCLK_BAUD       0x40    /* recv clock taken from BRG */
#define ZSWR11_RXCLK_DPLL       0x60    /* recv clock taken from DPLL */

#define ZSWR11_TXCLK_RTXC       0x00    /* xmit clock taken from RTxC* pin */
#define ZSWR11_TXCLK_TRXC       0x08    /* xmit clock taken from TRxC* pin */
#define ZSWR11_TXCLK_BAUD       0x10    /* xmit clock taken from BRG */
#define ZSWR11_TXCLK_DPLL       0x18    /* xmit clock taken from DPLL */

#define ZSWR11_TRXC_OUT_ENA     0x04    /* TRxC* pin will be an output */
                                        /* (unless it is being used above) */
#define ZSWR11_TRXC_XTAL        0x00    /* TRxC output from xtal oscillator */
#define ZSWR11_TRXC_XMIT        0x01    /* TRxC output from xmit clock */
#define ZSWR11_TRXC_BAUD        0x02    /* TRxC output from BRG */
#define ZSWR11_TRXC_DPLL        0x03    /* TRxC output from DPLL */

/*
 * Formula for Write Registers 12 and 13 (`Lower Byte of Baud Rate
 * Generator Time Constant' and `Upper Byte of ...').  Inputs:
 *
 *      f       BRG input clock frequency (in Hz) AFTER division
 *              by 1, 16, 32, or 64 (per clock divisor in WR4)
 *      bps     desired rate in bits per second (9600, etc)
 *
 * We want
 *
 *        f
 *      ----- + 0.5 - 2
 *      2 bps
 *
 * rounded down to an integer.  This can be computed entirely
 * in integer arithmetic as:
 *
 *      f + bps
 *      ------- - 2
 *       2 bps
 */
#define BPS_TO_TCONST(f, bps)   ((((f) + (bps)) / (2 * (bps))) - 2)

/* inverse of above: given a BRG Time Constant, return Bits Per Second */
#define TCONST_TO_BPS(f, tc)    ((f) / 2 / ((tc) + 2))

/*
 * Bits in Write Register 14 (`Miscellaneous Control Bits').
 * Bits 7 through 5 are taken as a unit and make up a `DPLL command'.
 */
#define ZSWR14_DPLL_NOOP        0x00    /* leave DPLL alone */
#define ZSWR14_DPLL_SEARCH      0x20    /* enter search mode */
#define ZSWR14_DPLL_RESET_CM    0x40    /* reset `clock missing' in RR10 */
#define ZSWR14_DPLL_DISABLE     0x60    /* disable DPLL (continuous search) */
#define ZSWR14_DPLL_SRC_BAUD    0x80    /* set DPLL src = BRG */
#define ZSWR14_DPLL_SRC_RTXC    0xa0    /* set DPLL src = RTxC* or xtal osc */
#define ZSWR14_DPLL_FM          0xc0    /* operate in FM mode */
#define ZSWR14_DPLL_NRZI        0xe0    /* operate in NRZI mode */

#define ZSWR14_LOCAL_LOOPBACK   0x10    /* set local loopback mode */
#define ZSWR14_AUTO_ECHO        0x08    /* set auto echo mode */
#define ZSWR14_DTR_REQ          0x04    /* DTR* / REQ* pin gives REQ* */
#define ZSWR14_BAUD_FROM_PCLK   0x02    /* BRG clock taken from PCLK */
                                        /* (else from RTxC* pin or xtal osc) */
#define ZSWR14_BAUD_ENA         0x01    /* enable BRG countdown */

/*
 * Bits in Write Register 15 (`External/Status Interrupt Control').
 * Most of these cause status interrupts whenever the corresponding
 * bit or pin changes state (i.e., any rising or falling edge).
 *
 * NOTE: ZSWR15_SDLC_FIFO & ZSWR15_ENABLE_ENHANCED should not be
 * set on an NMOS 8530. Also, ZSWR15_ENABLE_ENHANCED is only
 * available on the 85230.
 */
#define ZSWR15_BREAK_IE         0x80    /* enable break/abort status int */
#define ZSWR15_TXUEOM_IE        0x40    /* enable TX underrun/EOM status int */
#define ZSWR15_CTS_IE           0x20    /* enable CTS* pin status int */
#define ZSWR15_SYNCHUNT_IE      0x10    /* enable SYNC* pin/hunt status int */
#define ZSWR15_DCD_IE           0x08    /* enable DCD* pin status int */
#define ZSWR15_SDLC_FIFO        0x04    /* enable SDLC FIFO enhancements */
#define ZSWR15_ZERO_COUNT_IE    0x02    /* enable BRG-counter = 0 status int */
#define ZSWR15_ENABLE_ENHANCED  0x01    /* enable writing WR7' at reg 7 */

/*
 * Bits in Read Register 0 (`Transmit/Receive Buffer Status and External
 * Status').
 */
#define ZSRR0_BREAK             0x80    /* break/abort detected */
#define ZSRR0_TXUNDER           0x40    /* transmit underrun/EOM (sync) */
#define ZSRR0_CTS               0x20    /* clear to send */
#define ZSRR0_SYNC_HUNT         0x10    /* sync/hunt (sync mode) */
#define ZSRR0_DCD               0x08    /* data carrier detect */
#define ZSRR0_TX_READY          0x04    /* transmit buffer empty */
#define ZSRR0_ZERO_COUNT        0x02    /* zero count in baud clock */
#define ZSRR0_RX_READY          0x01    /* received character ready */

/*
 * Bits in Read Register 1 (the Zilog book does not name this one).
 */
#define ZSRR1_EOF               0x80    /* end of frame (SDLC mode) */
#define ZSRR1_FE                0x40    /* CRC/framing error */
#define ZSRR1_DO                0x20    /* data (receiver) overrun */
#define ZSRR1_PE                0x10    /* parity error */
#define ZSRR1_RC0               0x08    /* residue code 0 (SDLC mode) */
#define ZSRR1_RC1               0x04    /* residue code 1 (SDLC mode) */
#define ZSRR1_RC2               0x02    /* residue code 2 (SDLC mode) */
#define ZSRR1_ALL_SENT          0x01    /* all chars out of xmitter (async) */

/*
 * Read Register 2 in B channel contains status bits if VECTOR_INCL_STAT
 * is set.
 */

/*
 * Bits in Read Register 3 (`Interrupt Pending').  Only channel A
 * has an RR3.
 */
                        /*      0x80       unused, returned as 0 */
                        /*      0x40       unused, returned as 0 */
#define ZSRR3_IP_A_RX           0x20    /* channel A recv int pending */
#define ZSRR3_IP_A_TX           0x10    /* channel A xmit int pending */
#define ZSRR3_IP_A_STAT         0x08    /* channel A status int pending */
#define ZSRR3_IP_B_RX           0x04    /* channel B recv int pending */
#define ZSRR3_IP_B_TX           0x02    /* channel B xmit int pending */
#define ZSRR3_IP_B_STAT         0x01    /* channel B status int pending */

/*
 * Bits in Read Register 10 (`contains some miscellaneous status bits').
 */
#define ZSRR10_1_CLOCK_MISSING  0x80    /* 1 clock edge missing (FM mode) */
#define ZSRR10_2_CLOCKS_MISSING 0x40    /* 2 clock edges missing (FM mode) */
                        /*      0x20       unused */
#define ZSRR10_LOOP_SENDING     0x10    /* xmitter controls loop (SDLC loop) */
                        /*      0x08       unused */
                        /*      0x04       unused */
#define ZSRR10_ON_LOOP          0x02    /* SCC is on loop (SDLC/X.21 modes) */

/*
 * Bits in Read Register 15.  This register is one of the few that
 * simply reads back the corresponding Write Register.
 */
#define ZSRR15_BREAK_IE         0x80    /* break/abort status int enable */
#define ZSRR15_TXUEOM_IE        0x40    /* TX underrun/EOM status int enable */
#define ZSRR15_CTS_IE           0x20    /* CTS* pin status int enable */
#define ZSRR15_SYNCHUNT_IE      0x10    /* SYNC* pin/hunt status int enable */
#define ZSRR15_DCD_IE           0x08    /* DCD* pin status int enable */
                        /*      0x04       unused, returned as zero */
#define ZSRR15_ZERO_COUNT_IE    0x02    /* BRG-counter = 0 status int enable */
                        /*      0x01       unused, returned as zero */

#endif  /*  Z8530REG_H  */