The Channel Definition Block
Whenever a channel is opened, a channel definition block is allocated in the common heap. This block contains a certain amount of information regarding said channel. Different channel types have different channel definition blocks, but all channels have the first $18 bytes defined as the block header.
Block Header
| Offset | Size | QDOS Mnemonic | SMS Mnemonic | Description |
|---|---|---|---|---|
| $00 | Long | CH_LEN | CHN_LEN | Size of this channel definition block |
| $04 | Long | CH_DRIVR | CHN_DRVR | Address of the driver linkage block |
| $08 | Long | CH_OWNER | CHN_OWNR | Job id of the owner of this channel |
| $0C | Long | CH_RFLAG | CHN_RFLG | See note below. |
| $10 | Word | CH_TAG | CHN_TAG | Channel tag |
| $12 | Byte | CH_STAT | CHN_STAT | See note below |
| $13 | Byte | CH_ACTN | CHN_ACTN | Action code. (Value in D0 for last TRAP on this channel) |
| $14 | Long | CH_JOBWT | CHN_JBWT | Job id of the job waiting for I/O on this channel |
Notes
- CH_RFLG - QDOS Companion says that this is the location to be set when space released. SMS states that it is the location to be cleared when channel is closed.
- CH_STAT - There is a difference between QDOS Companion and the SMSQ documentation about CH_STAT, as follows:
| Value | QDOS Companion | SMSQ Documentation |
|---|---|---|
| 1 | Waiting | |
| 0 | Ok | OK |
| -1 | A1 has been absolute | waiting AND A1 is relative A6 |
| -128 | A1 passed relative to A6 | |
| other negatives | Waiting |
Definitions
As stated above, different channel types have different definition blocks. The following tables give details of the different definitions.
Pipe Driver
| Offset | Size | QDOS Mnemonic | SMS Mnemonic | Description |
|---|---|---|---|---|
| $18 | Long | CH_QIN | CHN_QIN | Pointer to input queue (or 0 if output) |
| $1C | Long | CH_QOUT | CHN_QOUT | Pointer to output queue (or 0 if input) |
Directory Drivers
| Offset | Size | QDOS Mnemonic | SMS Mnemonic | Description |
|---|---|---|---|---|
| $18 | Long | FS_NEXT | CHN_LINK | Link to next channel block |
| $1C | Byte | FS_ACCES | CHN_ACCS | Access mode (D3 on OPEN) |
| $1D | Byte | FS_DRIVE | CHN_DRID | Drive ID |
| $1E | Word | FS_FILNR | CHN_QDID | File number on drive (QDOS) |
| $20 | Word | FS_NBLOCK | CHN_FPOS | Block containing next byte |
| $22 | Word | FS_NBYTE | Next byte from block | |
| $24 | Word | FS_EBLOCK | CHN_FEOF | Block number containing byte after EOF |
| $26 | Word | FS_EBYTE | Byte after EOF | |
| $28 | Long | FS_CBLOCK | CHN_CSB | Current slave block |
| $2C | Byte | FS_UPDT | CHN_UPDT | Set when file updated |
| $2D | Byte | CHN_USEF | File use flags | |
| $32 | String | FS_FNAME | CHN_NAME | Filename |
| $58 | Long | CHN_DDEF | Pointer to physical definition block | |
| $5C | Word | CHN_DRNR | Drive number | |
| $5E | Word | CHN_FLID | File ID | |
| $5E | Word | CHN_SCTL | Sector length (direct sector IO) | |
| $60 | $40b | CHN_OPWK | $40 bytes of working space for open | |
| $62 | Word | CHN_SDID | Directory ID | |
| $64 | Long | CHN_SDPS | Directory entry position | |
| $68 | Long | CHN_SDEF | Directory end of file | |
| $70 | $30b | CHN_SPR | Spare | |
Network Driver
The mnemonics are the same for SMS and QDOS
| Offset | Size | Mnemonic | Description |
|---|---|---|---|
| $18 | Byte | NET_HDR | Destination station number |
| $19 | Byte | NET_SELF | Number of station which opened the channel |
| $1A | Byte | NET_BLKL | Lsb of data block number |
| $1B | Byte | NET_BLKH | Msb of data block number |
| $1C | Byte | NET_TYPE | Packet type: 0 for data, 1 last packet (EOF) |
| $1D | Byte | NET_NBYT | Number of bytes in data block |
| $1E | Byte | NET_DCHK | Data checksum |
| $1F | Byte | NET_HCHK | Header checksum |
| $20 | $FFb | NET_DATA | Data block |
| $11F | Byte | NET_RPNT | Pointer to current position in data block |
Screen Driver
The mnemonics are the same for SMS and QDOS
| Offset | Size | Mnemonic | Description |
|---|---|---|---|
| $18 | Word | SD_XMIN | Window LHS |
| $1A | Word | SD_YMIN | |
| $1C | Word | SD_XSIZE | Window size |
| $1E | Word | SD_YSIZE | |
| $20 | Word | SD_BORWD | Border width |
| $22 | Word | SD_XPOS | Cursor position |
| $24 | Word | SD_YPOS | |
| $26 | Word | SD_XINC | Cursor increment |
| $28 | Word | SD_YINC | |
| $2A | 2*Long | SD_FONT | Font adresses |
| $32 | Long | SD_SCRB | Base address of screen |
| $36 | Long | SD_PMASK | Paper colour mask |
| $3A | Long | SD_SMASK | Strip colour mask |
| $3E | Long | SD_IMASK | Ink colour mask |
| $42 | Byte | SD_CATTR | Character attributes |
| $43 | Byte | SD_CURF | Cursor flag |
| $44 | Byte | SD_PCOLR | Paper colour byte |
| $45 | Byte | SD_SCOLR | Strip colour byte |
| $46 | Byte | SD_ICOLR | Ink colour byte |
| $47 | Byte | SD_BCOLR | Border colour byte |
| $48 | Byte | SD_NLSTA | New line status |
| $49 | Byte | SD_FMOD | Fill mode |
| $4A | Float | SD_YORG | Graphics window y-origin |
| $50 | Float | SD_XORG | Graphics window x-origin |
| $56 | Float | SD_SCAL | Graphics scale factor |
| $5C | Long | SD_FBUF | Pointer to fill buffer |
| $60 | Long | SD_FUSE | Pointer to user defined fill vectors |
| $64 | Word | SD_LINEL | Line length in bytes |
Note
SD_CATTR has the following meanings:
| Bit | Meaning |
|---|---|
| 0 | Underline mode |
| 1 | Flash (mode 8 only) |
| 2 | Transparent background |
| 3 | XOR mode |
| 4 | Double height characters |
| 5 | Extended width characters |
| 6 | Double width characters (or mode 8) |
| 7 | Graphics positioned character |
Serial Ports
The mnemonics are the same for SMS and QDOS
| Offset | Size | Mnemonic | Description |
|---|---|---|---|
| $18 | Word | SER_CHNQ | Port number |
| $1A | Word | SER_PAR | Parity: 0 none, 1 odd, 2 even, 3 mark, 4 space |
| $1C | Word | SER_THSX | Transmit handshake flag: <1 ignore, 0 handshake |
| $1E | Word | SER_PROT | Protocol flag: -1 for R, 0 for Z, +1 for C |
| $20 | $62b | SER_RXQ | Receive queue header then queue |
| $82 | $62b | SER_TXQ | Transmit queue header then queue |
The Pointer Environment
The pointer environment further extends the channel definition block for console channels, but in a downward direction prior to the header block detailed above. The layout of these extra fields is as follows.
The new format consists of the header as before then the new extra section of $30 bytes which is immediately followed by the standard screen driver block described earlier. The standard block will now, of course, be $30 bytes later. To make easy access to this block the Trap #3 routine SD_EXTOP sets the value of A0 to be $30 bytes larger than formerly. This means that programs using SD_EXTOP to access the standard block of screen channel data can use SD_EXTOP without the need to check and make allowance for the presence of the Pointer Environment.
In the following table Offset is the amount to be added to A0 when SD_EXTOP is used.
The mnemonics are those for SMS. There is no equivalent for QDOS.
| Offset | Size | Mnemonic | Description |
|---|---|---|---|
| -$18 | Word | SD_XHITS | x hit size |
| -$16 | Word | SD_YHITS | y hit size |
| -$14 | Word | SD_XHITO | x hit origin (screen co-ordinates) |
| -$12 | Word | SD_YHITO | y hit origin (screen co-ordinates |
| -$10 | Word | SD_XOUTS | x outline size |
| -$0E | Word | SD_YOUTS | y outline size |
| -$0C | Word | SD_XOUTO | x outline origin (screen co-ordinates) |
| -$0A | Word | SD_YOUTO | y outline origin (screen co-ordinates} |
| -$08 | Long | SD_PRWLB | Primary link list bottom up (primary window) |
| -$08 | Long | SD_PPRWN | Pointer to primary window (secondary window) |
| -$04 | Long | SD_PRWLT | Primary link list top down (primary window) |
| $00 | Long | SD_SEWLL | Secondary window list pointer |
| $04 | Long | SD_WSAVE | Window save area base |
| $08 | Long | SD_WSSIZ | Size of window save area |
| $0C | Long | SD_WWDEF | Pointer to window working definition |
| $10 | Byte | SD_WLSTT | Window lock status |
| $11 | Byte | SD_PRWIN | Primary window status |
| $12 | Byte | SD_WMODE | Window mode |
| $13 | Byte | SD_MYSAV | True if save area is mine |
| $14 | Byte | SD_WMOVE | Window move/query flag |
| $16 | Word | Border Colour (GD2) | |
Notes
- The window lock status (SD_WLSTT) is -1 locked, 0 unlocked and 1 no lock.
- The primary window status (SD_PRWIN) has bit 7 set for a primary window and bit 0 set if managed (ie IOP_OUTL called).
- The window/move query flag is D2 from IOP_RPTR.
GD2 Colours
GD2 colour modes use one word per pixel unlike the modes 4 and 8 which can pack eight pixels into one word. This requires a re-definition of some items as follows.
- The paper, strip and ink colour masks in the standard block contain two colours. These differ if the colour is a stipple and are the same if not.
- The bytes SD_PCOLR, SD_SCOLR and SD_ICOLR contain either the normal mode 4/8 colour or a code showing the type of stipple.
- $00 is no stipple.
- $20 is stipple 0.
- $60 is stipple 1.
- $A0 is stipple 2.
- $E0 is stipple 3.
- For a border, SD_BCOLR is either the mode 4/8 colour or a code showing the type of border.
- $00 shows a solid GD2 colour.
- $80 shows the special border.
- The border colour itself, or the code if the border is special, is held in the last word in the extra block shown above.
george.gwilt