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SPECIFICATION FOR MS-DOS KERMIT SYSTEM-DEPENDENT MODULES
by Jeff Damens, Columbia University
This document applies to Verson 2.28 of MS-DOS Kermit, and it has some
updates at the end for Version 2.29. It has not been updated for
version 2.30.
All the system-independent global data structures used in Kermit-MS are defined
in the file MSDEFS.H.
The routine MSXxxx.ASM contains system-dependent support for system xxx, except
for terminal emulation, which is in MSYxxx.ASM, described below.
The routines in the MSX module may change any registers but the stack pointer
and segment registers, unless otherwise noted. A routine that returns via a
RET instruction is said to return normally; a routine that skip returns is one
that returns to three bytes past the normal return address.
Global variables that must be defined in the system-dependent module:
XOFSNT byte. This should be set to a non-zero value if we are doing
flow control and have sent an XOFF character to the remote
host, zero otherwise.
MACHNAM byte. A $-terminated string identifying the machine this ver-
sion of Kermit is for; it is printed when Kermit starts up.
SETKTAB byte. A keyword table associating terminal key names to 16-bit
scan code values, used in the set key command. If the kermit
version can accept arbitrary decimal values as scan codes, the
word "SCAN" should appear in the table with a scan value of -1.
If key redefinition is not implemented, the first byte of the
table should be a zero.
SETKHLP byte. A $-terminated string to be printed when ? is typed in
the SET KEY command. This is usually simply a list of the key
names in SETKTAB. SETKHLP must be defined even if key
redefinition is not implemented, to satisfy the linker; if key
redefinition is not implemented, SETKHLP will never be dis-
played.
COUNT word. The number of characters in the serial input buffer, if
known. This is how Kermit knows to send an XON if the serial
handler has sent an XOFF. If the number of characters in the
buffer isn't known, COUNT should be 0.
These are the required entry points for the system dependent dependent module
MSXxxx.ASM.
SERINI
Parameters None.
Returns Normally, no return value.
Description Perform any initialization that must be done before the serial
port can be used, including setting baud rate, interrupt vec-
tors, etc. Parity and baud rate should be set according to the
values in the PORTINFO structure. The external variable
PORTVAL points to the PORTINFO structure for the current port.
Calling SERINI more than once without an intervening call to
SERRST should have no effect.
SERRST
Parameters None.
Returns Normally, no return value.
Description Undoes any initialization done by SERINI, including resetting
the serial port, restoring any interrupt vectors changed by
SERINI, etc. Calling this more than once without an interven-
ing call to SERINI should be harmless.
CLRBUF
Parameters None.
Returns Normally, no return value.
Description Remove and discard from the serial port's input buffer any
characters sent by the remote host that have not yet been read
by Kermit, and set COUNT to 0. This is used before a file
transfer to flush NAK's that accumulate in the buffer when the
remote host is in server mode.
OUTCHR
Parameters A character in AH.
Returns Skip returns if the character has been transmitted; returns
normally if the character can not be transmitted because of a
hardware error.
Description Sends the character in AH out the currently selected serial
port. OUTCHR can assume that SERINI will have been called
previously. OUTCHR should call the external routine DOPAR to
set the parity of the character if the communications hardware
doesn't automatically set parity. Flow control should be
honored; the external variable PORTVAL contains a pointer to a
PORTINFO structure (as defined in MSDEFS.H) containing the cur-
rent flow control definitions.
COMS
Parameters None.
Returns Normally if a parse error is encountered, skip returns other-
wise.
Description Called by the SET PORT command. On a machine with multiple
serial ports, COMS should parse for the name or number of a
serial port and make that the port used by succeeding calls to
SERINI, PRTCHR, OUTCHR, and SERRST. It should set the external
variable PORTVAL to point to one of the external port struc-
tures PORT1 or PORT2, and set COMFLG in the FLAGS structure to
1 for port one, 0 for port 2. For implementations that use
only one serial port, COMS should print a message to that ef-
fect and skip return.
VTS
Parameters None.
Returns Normally if a parse error is encountered, skip returns other-
wise.
Description Parses for an ON or OFF, sets HEATH-19 emulation while in ter-
minal emulation appropriately. The VTFLG field of the FLAGS
structure should be set non-zero if HEATH-29 emulation is on,
zero otherwise. If HEATH-19 emulation is not done, VTS should
print a message and skip return.
DODEL
Parameters None.
Returns Normally, no return value.
Description Erases the character immediately to the left of the cursor from
the screen, then backs up the cursor.
CTLU
Parameters None.
Returns Normally, no return value.
Description Move the cursor to the left margin, then clear the line.
CMBLNK
Parameters None.
Returns Normally, no return value.
Description Clears the screen and homes the cursor.
LOCATE
Parameters None.
Returns Normally, no return value.
Description Homes the cursor.
LCLINI
Parameters None.
Returns Normally, no return value.
Description Performs any system-dependent initialization required by this
implementation.
PRTCHR
Parameters None.
Returns Normally, with the next character from the currently selected
serial port in AL. Skip returns if no character is available.
Description Reads the next character from the current serial port. PRTCHR
can assume SERINI has been called previously, and should handle
flow control correctly.
DOBAUD
Parameters None.
Returns Normally, no return value.
Description Sets the baud rate for the current port. The baud rate should
be obtained from the BAUD field of the PORTINFO structure,
pointed to by the external variable PORTVAL.
CLEARL
Parameters None.
Returns Normally, no return value.
Description Clears from the cursor to the end of the current line.
DODISK
Parameters None.
Returns Normally, no return value.
Description Sets the external variable DRIVES to the number of disk drives
attached to the machine.
GETBAUD
Parameters None.
Returns Normally, no return value.
Description Store current baud rate of the currently selected port in the
BAUD field of the current PORTINFO structure, which is pointed
to by PORTVAL. If the baud rate is to default to a particular
value, this routine can store that value into the BAUD field
instead.
BEEP
Parameters None.
Returns Normally, no return value.
Description Rings the terminal bell.
PUTHLP
Parameters A pointer to a string in AX.
Returns Normally, no return value.
Description Writes the null-terminated string given in AX to the terminal.
This is used to display help and status messages. The IBM and
Rainbow versions write the string in a reverse video box.
PUTMOD
Parameters A pointer to a string in AX.
Returns Normally, no return value.
Description Writes the null-terminated string given in AX to the last line
of the screen, in inverse video if possible.
CLRMOD
Parameters None.
Returns Normally, no return value.
Description Clears the line written by PUTMOD.
POSCUR
Parameters Row in DH, column in DL.
Returns Normally, no return value.
Description Positions the cursor to the row and column given in DX. Rows
and columns both originate at 0 (not 1!).
SENDBR
Parameters None.
Returns Normally, no return value.
Description Send a break to the current serial port.
SHOWKEY
Parameters Pointer to a terminal argument block in AX (see TERM below).
Returns Normally, with a string pointer in AX and the length of the
string in CX.
Description Called by the SHOW KEY command. Reads a key from the terminal
and returns a string containing implementation-dependent infor-
mation about the key. In the usual case, the string contains
the key's (machine-dependent) scan code, and the key's defini-
tion (if any) from the terminal argument block. The length of
the returned string should be returned in CX. The string may
contain any characters; unprintable characters will be quoted
when the string is printed. If the implementation does not
support key redefinition, SHOWKEY may return a static string
saying so.
TERM
Parameters Pointer to terminal argument block in AX.
Returns Normally, no return value.
Description Do terminal emulation, based on argument block described
below...
The following entry points were added for version 2.29 by Joe R. Doupnik of
Utah State University (May 1986):
DTRLOW
Parameters None.
Returns Return-skip normally or just Return if command not confirmed.
Description Parses HANGUP command and calls local procedure SERHNG to lower
modem control lines DTR and RTS. Most MS Kermits have not im-
plemented SERHNG; a "not implemented" message results in these
cases.
DUMPSCR
Parameters None.
Returns Normally.
Description Copies text from the screen to a file. Word DMPNAME holds the
address (offset in data segment) of a zero terminated string of
the filename or device; the default string is KERMIT.SCN;
MSSSET stores this string. Method of copying is to capture the
screen to a buffer and read out the text to a file, with lines
trimmed of trailing blanks and terminated by CR/LF. A Form Feed
ends the file. The filename is checked for collision with sys-
tem, readonly, subdirectory types etc and a complaint message
is displayed if such a collision occurs. The file is opened
and closed for each screen dump operation. Current implemen-
tations are on IBM and Rainbow machines, and they append new
material to a pre-existing file. On other systems a simple
Return is done.
IHOSTR
Parameters None.
Returns Normally.
Description Initializes the remote host for our reception of a file by
sending the flow-on character (XON normally) to release any
held data. Called by receive-file code just after initing the
serial port.
IHOSTS
Parameters None.
Returns Normally.
Description Initializes the host for our sending of a file by sending the
flow-on character (XON normally) to release any held data, such
as NAKs, flushes the serial port input buffer, waits one second
(by calling SLEEP), and exits if the buffer is empty. Other-
wise, the cycle of clear buffer, sleep one second, check buffer
is repeated. Called by send-file routine just after initializ-
ing the serial port.
VTS
Parameters None.
Returns Skip-return normally or just Return if parser error.
Description Parses SET TERM commands. The IBM version has many keywords
which are further parsed and cause jumps to action routines
within this procedure. Non-IBM Kermits usually parse the
keywords ON and OFF, for Heath-19 emulation or not. Common to
all MS Kermits is the setting of global byte FLAGS.VTFLG in-
dicating the terminal emulation type (types are defined in the
header file MSSDEF.H). For the VT102 emulator in the IBM Kermit
VTS also writes into structure VTEMU to pass information to the
emulator about colors, tabstops, line-wrap, and other Set Term
parameters and controls global byte REFRESH passed to module
MSYIBM to govern screen refresh methodology. Small local pars-
ing support procedures are included here.
Structure VTEMU is defined in header file MSSDEF.H and contains
the following fields:
VTFLGST Byte. Holds VT102 setup flag bits, which when
set mean -
VSNEWLINE (01H)
ANSI Newline mode active
VSWRAP (02H)
Line wrap is active
VSSHIFT3 (04H)
Sharp sign (#) replaced by Pound Sterling
VSKEYCLICK (08)
Keyclick on
VSMARGINBELL (10H)
Sound bell when cursor passes column 72
VSCURSOR (20H)
Cursor is a block (vs underline)
VSSCREEN (40H)
Screen is to be reverse video
A constant VSDEFAULTS is defined in the header
file as the OR of bits above which is used by
the emulator at Kermit startup time in lieu of
Set Term.
VTTBS Word. Holds address (offset in data segment) to
default tabstop byte array. This array is lo-
cated in file MSZIBM.
VTTBST Word. Holds address (offset in data segment) to
active tabstop byte array. This array is lo-
cated in file MSZIBM.
ATT_PTR Word. Pointer (offest in data segment) to video
attributes byte pair (which is stored in file
MSZIBM).
Further, global byte FLAGS.VTFLG holds the kind of terminal being emulated.
Kinds are defined in the header file as constants:
TTGENERIC 0 no emulation
TTHEATH 1 Heath-19
TTVT52 2 VT52 submode of VT102
TTVT102 3 VT102
TTTYPES 4 number of types defined above.
VTSTAT
Parameters Enter with register DI pointing to status buffer STTBUF.
Returns Register CX counting the right most column used in status dis-
play and register DI 40 bytes larger that at entry. Uses nor-
mal Return, not Skip-return.
Description Displays Status information about terminal emulator. Called by
procedure STAT0 in file MSSSET. This procedure is similar to
normal Status ones except the data items are from structure
VTEMU. Command macros for VTSTAT are defined in file MSXxxx.
VTSTAT writes the status information directly to the screen and
returns to STAT0 with character in line pointer register DI set
40 bytes larger than when entered (even though several lines
may have been displayed) and register CX holding the number of
chars shown on the last line. Non-IBM Kermits just do a simple
Return. Normally VTSTAT is the last Status item called by
STAT0.
Terminal emulation is supplied in the system dependent files MSXxxx, MSYxxx,
and possibly MSZxxx, depending on the machine. The terminal "argument block"
passed to procedure TERM is listed below; but note that the VT102 emulator for
IBM machines uses an additional global structure VTEMU. The terminal argument
block passed to the terminal emulator has the following fields:
FLGS Byte containing flags. Flags are:
SCRSAM (80H) If on, the terminal emulator shouldn't
re-display the screen when entered.
CAPT (40H) Capture output. If on, the routine passed in
field CAPTR is called with each character sent
to the screen.
EMHEATH (20H) On if terminal emulation is active. Obsolete.
The preferred method is to examine byte
FLAGS.VTFLG for the terminal type.
HAVTT (10H) A key redefinition table is present.
TRNCTL (08H) Print control character X as ^X (useful for
debugging).
MODOFF (04H) Do not display emulator mode line if on.
LCLECHO (01H) Echo keyboard characters on the screen in ad-
dition to sending them to the port.
PRT Port to use for terminal emulation, used only in mode line.
This is just a copy of COMFLG in FLAGS.
COLS Number of columns on screen.
ROWS Number of rows on screen.
CAPTR Routine to call to with each character sent to the screen if
CAPT flag is on. Characters are passed in AL.
BELLD Bell divisor (used only on IBM).
KLEN Number of keys in key redefinition table, if HAVTT flag is on.
KTAB Address of key redefinition table. The key redefinition table
is a table of KLEN 16-bit scan codes. Each (machine dependent)
scan code represents a key that is redefined.
KRPL Address of key replacement table. The key replacement table
parallels the key redefinition table given in KTAB. Entries in
the replacement table are 16-bit pointers to redefinitions.
Each redefinition has a one-byte length, followed by the
definition.
ESCC Escape character (single byte). When this character is typed
to the emulator, it should return.
BAUDB byte. Bits describing the baud rate so it can be printed on
the mode line. This is a copy of the BAUD field in the POR-
TINFO structure. Currently used only on the IBM. See MSDEFS.H
for possible values.
PARITY byte. Current parity to print on the mode line. This is a
copy of PARFLG in the PORTINFO structure. Currently used only
on the IBM. See MSDEFS.H for possible values.