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bios.c
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bios.c
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/**************************************************************
*
* file: bios.c
*
* This file contains the BIOS to allow execution of CP/M-VAX
* on the MicroVAX-2000. The assumed system configuration is:
*
* - A MicroVAX-2000.
* - A BCC08 cable, which turns serial port #3 into a console.
*
* Currently, no disk I/O is performed. Stay tuned.
*
* Several things SHOULD be here, but are not. Initialization
* of the SCB is in boot.s, the final stage bootstrap. It should
* be here because the requirements of the SCB vary from model
* to model. As it is, a port to (say) a VAX-11/780 would require
* a bit of work in boot.s as well as changes here.
*
* revisions:
*
* 2005-03-07 rli: Split arch.s off from this file.
*
**************************************************************/
/******************
*
* TYPES
*
******************/
/***
*
* bios_dpb_t
*
* This is the disk parameter block. It describes a disk to
* the system.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
typedef struct bios_dpb_s {
unsigned short int spt; /* sectors per track */
unsigned char bsh; /* block shift factor */
unsigned char blm; /* block mask */
unsigned char exm; /* extent mask */
unsigned char reserved1;
unsigned short int dsm; /* number of blocks in disk */
unsigned short int drm; /* number of directory entries */
unsigned short int reserved2; /* initial allocation vector in -80 */
unsigned short int cks; /* size of checksum vector */
unsigned short int off; /* reserved tracks */
} bios_dpb_t;
/***
*
* bios_dph_t
*
* This is the disk parameter header. It contains pointers to the
* various data structures needed to run a disk.
*
* revisions:
*
* 2005-03-07 rli: original version.
*
***/
typedef struct bios_dph_s {
unsigned short *xlt; /* sector translation table address */
unsigned short int scratch[ 3 ]; /* scratch words used by BIOS */
unsigned char *dirbuf; /* scratch sector for directory use */
bios_dpb_t *dpb; /* address of disk parameter block */
unsigned char *csv; /* checksum vector */
unsigned char *alv; /* allocation vector */
} bios_dph_t;
/***
*
* bios_mrt_t
*
* This is the memory region table. It describes the RAM to the
* operating system.
*
* We're reserving a page below the start of the operating system
* to hold the initial stack.
*
* revisions:
*
* 2005-03-07 rli: original version.
*
***/
typedef struct bios_mrt_s {
unsigned short int count; /* number of regions in table */
void *base; /* base address of first region */
unsigned long int length; /* length of first region */
} bios_mrt_t;
/*******************
*
* GLOBALS
*
*******************/
/***
*
* bios_8inch_dpb
*
* This disk parameter block describes a standard 8" SSSD floppy
* diskette. We're currently using this format for a RAM disk.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
bios_dpb_t bios_8inch_dpb = {
26, /* 128-byte sectors per track */
3, /* block shift */
7, /* block mask */
0, /* extent mask */
0, /* reserved */
242, /* allocation blocks per disk - 1 */
63, /* number of directory entries - 1 */
0, /* reserved; initial allocation vector in CP/M-80 */
16, /* size of check vector */
2 /* track offset */
};
/***
*
* bios_dirbuf
*
* This is a scratch buffer used to hold sectors while the BDOS
* performs directory manipulation. It is shared between all
* of the disks.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
unsigned char bios_dirbuf[ 128 ];
/***
*
* bios_drivea_csv
*
* The system uses the check vector to determine whether or not
* a diskette has been changed. The vector contains one byte
* for each directory entry. The operating system forms a checksum
* across each directory entry when the disk is logged in to allow
* a diskette change to be detected.
*
* Each drive requires a separate check vector. This is the vector
* for drive A:, the 8" SSSD RAM disk.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
unsigned char bios_drivea_csv[ 64 ];
/***
*
* bios_drivea_alv
*
* This is the allocation vector for drive A:, the 8" SSSD RAM
* disk. The operating system uses this vector to locate free
* blocks when it needs to allocate a block to a file. The vector
* contains one bit for each block on the disk.
*
* Each drive requires a separate allocation vector.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
unsigned char bios_drivea_alv[ ( 242 / 8 ) + 1 ];
/***
*
* bios_8inch_xlt
*
* This is a sector translation table for the standard 8" SSSD
* format. Although we're using a RAM disk, we use the 8" SSSD
* format to allow us to load actual disk images, at least until
* we're running on an actual disk. Consequently, we need to
* use the standard sector skew.
*
* All drives of a given type may share a single translation table.
*
* revisions:
*
* 2003-03-07 rli: Added these comments.
*
***/
unsigned short int bios_8inch_xlt[ 26 ] = {
0, 6, 12, 18, 24, 4, 10, 16,
22, 2, 8, 14, 20, 1, 7, 13,
19, 25, 5, 11, 17, 23, 3, 9,
15, 21
};
/***
*
* bios_8inch_dph
*
* This is the disk parameter header for drive A:, the 8" SSSD RAM
* disk. It contains pointers to the other data structures needed
* to run a drive; when the BDOS selects a drive, it receives a
* pointer to this structure, which it uses to locate the others.
*
* Each drive needs its own disk parameter header.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
bios_dph_t bios_8inch_dph = {
bios_8inch_xlt, /* sector translation table */
0, 0, 0, /* scratch words */
bios_dirbuf, /* directory buffer */
&bios_8inch_dpb, /* disk parameter block */
bios_drivea_csv, /* checksum vector */
bios_drivea_alv /* allocation vector */
};
/***
*
* bios_currenttrack
*
* This variable holds the current track number; in other words,
* the last track number that was set by the BDOS using the BIOS SET
* TRACK function.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
unsigned int bios_currenttrack;
/***
*
* bios_currentdrive
*
* This variable holds the current drive number; in other words,
* the number of the most recently successfully selected disk
* drive.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
unsigned int bios_currentdrive;
/***
*
* bios_currentsector
*
* This variable holds the currently selected sector number; that
* is, the last sector number handed to the BIOS SET SECTOR
* function.
*
* revisions:
*
* 2005-03-07 rli: added these comments.
*
***/
unsigned int bios_currentsector;
/***
*
* bios_currentdmaaddress
*
* This variable holds the current DMA address; that is, the
* last DMA address handed to the BIOS SET DMA ADDRESS function.
*
* revisions:
*
* 2005-03-07 rli: added these comments.
*
***/
unsigned char *bios_currentdmaaddress;
/***
*
* bios_mrt
*
* The memory region table describes the TPA to the system. We're
* going to allocate memory from zero to the bottom of the system
* image to the TPA, less a page we're reserving right below
* the system for stack space. The system image (declared in
* boot.s) begins at start.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
***/
extern void start();
bios_mrt_t bios_mrt = {
1, /* one region in the table */
0, /* start address */
( (unsigned long int)start ) - 512 /* size */
};
/***
*
* bios_iobyte
*
* This variable contains the I/O byte, which is not currently
* implemented. Sure, we'll store it here and we'll read it back,
* but we aint using it to select any ports.
*
* revisions
*
* 2005-03-07 rli: added these comments.
*
***/
unsigned short int bios_iobyte;
/***
*
* FUNCTION 0: INITIALIZATION
*
* This routine is entered on cold boot and must initialize the
* BIOS.
*
* At the moment, all our initialization is done elsewhere, so
* there's nothing to be done here.
*
* revisions:
*
* 2005-03-07 rli: Updated tese comments.
*
* formal parameters:
*
* none.
*
* informal parameters:
*
* none
*
* return value:
*
* The default drive number and user number:
*
*
* 1098765432109876 54321098 76543210
* +----------------+--------+--------+
* |000000000000000 | | |
* +----------------+--------+--------+
* ^ ^
* | |
* | +-- default drive number
* +-- initial user number
*
* side effects:
*
* none.
*
***/
unsigned long int bios_boot( void )
{
return 0;
}
/***
*
* FUNCTION 1: WARM BOOT
*
* This function is called whenever a program terminates. Some
* reinitialization of the hardware or software might occur.
*
* Since we might be called from a user program, we don't know
* where the stack is. So re-initialize everything and start
* over. At some point, this will become inappropriate; someone
* will want an autostart command line executed on cold boot
* but not warm boot or whatnot.
*
* revisions:
*
* 2005-03-07 rli: rework to re-initialize the stack pointer.
*
* formal parameters:
*
* none.
*
* informal parameters:
*
* none.
*
* return value:
*
* doesn't return.
*
* side effects:
*
* The system is restarted.
*
***/
void bios_wboot( void )
{
extern void entry( void );
entry();
}
/***
*
* FUNCTION 2: CONSOLE STATUS
*
* This function returns the status of the currently assigned
* console device. It returns 0x00FF when a character is ready
* to be read or 0x0000 when no console characters are ready.
*
* Currently, we support only line number 3 of the DZ; we don't
* use the I/O byte.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
* formal parameters:
*
* none.
*
* informal parameters:
*
* A MicroVAX 2000 DZ at address 200A.0000.
*
* return value:
*
* - 0x0000: no characters are ready from the console.
*
* - 0x00ff: A character may be read from the console.
*
* side effects:
*
* none.
*
***/
unsigned short int bios_const( void )
{
/* We've disabled lines we're not interested in, so anything that
* comes in should be from the console.
*/
if( ( *(unsigned short int *)0x200A0000 ) & 0x80 )
return 0xff;
return 0;
}
/***
*
* FUNCTION 3: READ CONSOLE CHARACTER
*
* This function reads and returns the next console character.
* If no console character is ready, it waits until a character
* is typed before returning.
*
* Currently, we use only line 3 of the DZ; we ignore the I/O byte.
*
* revisions:
*
* 2005-03-07 rli: Added these comments.
*
* formal parameters:
*
* none.
*
* informal parameters:
*
* A MicroVAX 2000 DZ at address 200A.0000.
*
* return value:
*
* - character read from the console.
*
* side effects:
*
* none.
*
***/
unsigned char bios_conin( void )
{
while( !bios_const() );
return ( *(unsigned short int *)0x200A0004 ) & 0x7f;
}
/***
*
* FUNCTION 4: WRITE CONSOLE CHARACTER
*
* This function sends a character to the console output device.
*
* Currently, we support only line 3 of the DZ; we're ignoring the
* I/O byte.
*
* revisions:
*
* 2005-03-07 rli: added these comments.
*
* formal parameters:
*
* - victim: the character to be displayed.
*
* informal parameters:
*
* A MicroVAX 2000 DZ at address 200A.0000.
*
* return value:
*
* none.
*
* side effects:
*
* Transmission is disabled for all lines except line 3.
*
***/
void bios_conout( unsigned char victim )
{
/* Ensure transmission is enabled for line 3 and only line 3. That
* way, when the DZ is ready to send, it's ready to send to the
* console.
*/
*(unsigned short int *)0x200A0008 = 8;
/* Wait for the line to be ready to print.
*/
while( !( ( *(unsigned short int *)0x200A0000 ) & 0x8000 ) ) ;
/* Send the character.
*/
*(unsigned short int *)0x200A000C = victim;
}
/***
*
* FUNCTION 5: LIST CHARACTER OUTPUT
*
* This character sends an ASCII character to the currently
* designated listing device. If your list device requires some
* communication protocol, it must be handled here.
*
* formal parameters:
*
* - victim: the character to be sent to the printer.
*
* return value:
*
* none.
*
***/
void bios_list( unsigned char victim )
{
}
/***
*
* FUNCTION 6: AUXILIARY OUTPUT
*
* This function sends an ASCII character to the currently assigned
* auxiliary output device.
*
* formal parameters:
*
* - victim: the character to be sent to the punch.
*
* return value:
*
* none.
*
***/
void bios_punch( unsigned char victim )
{
}
/***
*
* FUNCTION 7: AUXILIARY INPUT
*
* This function reads the next character from the currently
* assigned auxiliary input device. It reports an end-of-file
* condition by returning an ASCII CTRL-Z (0x1a).
*
* formal parameters:
*
* none.
*
* return value:
*
* - The character read from the reader.
*
***/
unsigned char bios_reader( void )
{
return 0x1a;
}
/***
*
* FUNCTION 8: HOME
*
* This function returns the disk head of the currently selected
* disk to the track 00 position. If your controller does not have
* a special feature for finding track 00, you can translate teh
* call to a SETTRK function with a parameter of 0.
*
* formal parameters:
*
* none.
*
* return value:
*
* none.
*
***/
void bios_home( void )
{
bios_currenttrack = 0;
}
/***
*
* FUNCTION 9: SELECT DISK DRIVE
*
* This function selects the specified disk drive for further
* operations. The parameter contains 0 for drive A, 1 for drive B,
* up to 15 for drive P.
*
* On each disk select, this function returns the address of the
* selected drive's Disk Parmaeter Header.
*
* If there is an attempt to select a nonexistent drive, this
* functions 0 as an error indicator. Although the function must
* return the header address on each call, it may be advisable to
* postpone the actual physical disk select operation until an I/O
* function (seek, read, or write) is performed. Disk select
* operations can occur withou; a subsequent disk operation. Thsu,
* doing a physical selecte ach time this funciton is called may be
* wasteful of time.
*
* On entry to the Select Disk Drive function, if the least
* significant bit in the second parameter is zero, the disk is not
* currently logged in. If the disk drive is capable of handling
* varying media (such as single and double-sided disks, single- and
* double-density, and so on), the BIOS should check the type of
* media currnetly installed and set up the Disk Parameter Block
* accordingly at this time.
*
* formal parameters:
*
* - drive: the number of the drive to be selected.
*
* - logged: indicates whether the drive is currently logged in.
*
* return value:
*
* - 0: The drive number is invalid.
*
* - else: A pointer to the DPH for the drive.
*
***/
bios_dph_t *bios_seldsk( unsigned char drive, unsigned char logged )
{
switch( drive ) {
case 0:
bios_currentdrive = drive;
return &bios_8inch_dph;
default:
return 0;
}
}
/***
*
* FUNCTION 10: SET TRACK NUMBER
*
* This function specifies the disk track number for use in
* subsequent disk accesses. The track number remains valid until
* either another Function 10 or a Function 8 (Home) is performed.
*
* You can choose to physically seek to the selected track at this
* time, or delay the physical seek until the next read or write
* actually occurs.
*
* The track number can range from 0 to the maximum track number
* supported by the physical drive. However, the maximum track
* number is limited to 65535 by the fact that it is being passed
* as a 16-bit quantity. Standard floppy disks have tracks number
* from 0 to 76.
*
* formal parameters:
*
* - track: The track number.
*
* return value:
*
* none.
*
***/
void bios_settrk( unsigned short int track )
{
bios_currenttrack = track;
}
/***
*
* FUNCTION 11: SET SECTOR NUMBER
*
* This function specifies the sector number for subsequent disk
* accesses. This number remains in effect until another function
* 11 is performed.
*
* Th function select actual (unskewed) sector numbers. If skewing
* is appropriate, it will have previously been done by a call to
* Function 16. You can send this information to the controller at
* this point or delay sector selection until a read or write
* operation occurs.
*
* formal parmaeters:
*
* - sector: the sector to be used for subsequent I/O.
*
* return value:
*
* none.
*
***/
void bios_setsec( unsigned short int sector )
{
bios_currentsector = sector;
}
/***
*
* FUNCTION 12: SET DMA ADDRESS
*
* This function specifies teh DMA address for subsequent read or
* write operations. Note that the controller need not actually
* support DMA (direct memory access). The BIOS will use the
* 128-byte area starting at the selected DMA address for the
* memory buffer during the following read or write operations.
* This function can be called with either an even or an odd
* address for a DMA buffer.
*
* formal parameters:
*
* - dmaaddress: pointer to the sector buffer.
*
* return value:
*
* none.
*
***/
void bios_setdma( void *dmaaddress )
{
bios_currentdmaaddress = dmaaddress;
}
/*** bios_diskimage
*
* This array contains the disk image.
*
***/
extern unsigned char bios_diskimage[];
/***
*
* FUNCTION 13: READ SECTOR
*
* After the drive has been selected, the track has been set, the
* sector has been set, and teh DMA address has been specified, the
* read function uses these parameters to read one sector and
* returns the error code.
*
* Currently, CP/M-68K responds only to a zero or nonzero return
* code value. Thus, if the return value is zero, CP/M-68K assumes
* that the disk operation completed properly. If an error occurs,
* however, the BIOS should attempt at least ten retries to see if
* the error is recoverable.
*
* formal parameters:
*
* none.
*
* return value:
*
* - 0: success.
*
* - 1: failure.
*
***/
unsigned short int bios_read( void )
{
int i;
int start;
start = (( bios_currenttrack * 26 ) + bios_currentsector ) * 128;
for( i = 0; i < 128; i++ )
bios_currentdmaaddress[ i ] = bios_diskimage[ start + i ];
return 0;
}
/***
*
* FUNCTION 14: WRITE SECTOR
*
* This function is used to write 128 bytes of data from the
* currently selected DMA buffer to the currently selected sector,
* track, and disk. The parameter indicates whether the write is an
* ordinary write operation or whether there are special
* considerations.
*
* If the parameter is 0, this is an ordinary write operation. If
* it is 1, this is a write to a directory sector, and the write
* should be physically completed immediately. If the parmaters is
* 2, this is a write to teh first sector of a newly allocated
* block of the disk.
*
* formal parameters:
*
* - typecode: the type of the write.
*
* return value:
*
* - 0: success.
*
* - 1: error.
*
***/
unsigned short int bios_write( unsigned short int typecode )
{
int i;
int start;
start = (( bios_currenttrack * 26 ) + bios_currentsector ) * 128;
for( i = 0; i < 128; i++ )
bios_diskimage[ start + i ] = bios_currentdmaaddress[ i ];
return 0;
}
/***
*
* FUNCTION 15: RETURN LIST STATUS
*
* This function returns the status of the list device, either 0
* when the list device is not ready to accept a character or 0xff
* when a character can be sent to the list device.
*
* formal parameters:
*
* none
*
* return value:
*
* - 0: printer is not ready to accept a character.
*
* - 0xff: printer is ready to accept a character.
*
***/
unsigned short int bios_listst( void )
{
return 0xff;
}
/***
*
* FUNCTION 16: SECTOR TRANSLATE
*
* This function performs logical-to-physical sector translation.
* The Sector Translate function receives a logical sector number.
* The logical sector number can range from 0 to the number of
* sectors per track - 1. Sector Translate also receives the
* address of teh translate table. The logical sector number is
* used as an index into the translate table. The resulting
* physical sector number is returned.
*
* If the pointer to the translate table is null, implying that
* there is no translate table, the original sector number is
* returned. Note that other algorithms are possible; in
* particular, it is common to increment the logical sector number
* in order to convert the logical range of 0 to n-1 into the
* physical range of 1 to n. Sector Translate is always called by
* the BDOS, whether the translate table address in the Disk
* Parameter Header is zero or nonzero.
*
* formal parameters:
*
* - sector: logical sector number.
*
* - table: pointer to sector number translation table.
*
* return value:
*
* physical sector number.
*
***/
unsigned short int bios_sectran( unsigned short int sector,
unsigned short int *table )
{
if( table == 0 ) return sector;
return table[ sector ];
}
/***
*
* FUNCTION 17: There is NO function 17
*
***/
/***
*
* FUNCTION 18: GET ADDRESS OF MEMORY REGION TABLE
*
* This function returns the address of the Memory REgion Table
* (MRT). For compatibility with other CP/M system, CP/M-68K
* maintains a Memory Region Table. However, it contains only one
* region, the Transient Program Area (TPA).
*
* formal parameters:
*
* none.
*
* return value:
*
* A pointer to the memory region table.
*
***/
bios_mrt_t *bios_getmrt( void )
{
return &bios_mrt;
}
/***
*
* FUNCTION 19: GET I/O BYTE
*
* This function returns the currnet value of the logical to
* physical input/output device byte (I/O byte). This 8-bit value
* associates physical devices with CP/M-68k's four logical
* devices.
*
* NOTE: Even though this is a byte value, we are using
* word references. The upper byte should be zero.
*
* formal parameters:
*
* none.
*
* return value:
*
* a copy of the I/O byte.
*