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.