IBM PC X-talk. Version 1.01 A. Howitt Sept. 1984. Introduction : The IBM PC X-talk program is a communications package using asynchronous protocols to provide a utility for transferring files to and from the Edinburgh Multi-Access System (EMAS) via a Terminal Control Processor (TCP). The program was written originally for the Sirius computer by Robin E. Day of Business Studies and hence the user interface is similar on both machines. In order to run the program DOS Version 2.00 operating system must be used with the extended screen and keyboard control device driver. This can be accomplished by placing the command : DEVICE=ANSI.SYS in your CONFIG.SYS (configuration) file. (See DOS manual Chap. 9 & 13.) After rebooting the system it will be possible to establish communication with EMAS but before files can be transfered two OPTION settings will be required in your EMAS process. 1). Insert file MICROS.EMASLIB. 2). Set interactive terminal input buffer size to 16 Kbytes. This is achieved by the following sequence in response to the EMAS prompt : Command:OPTION(SEARCHDIR=MICROS.EMASLIB) Command:OPTION(ITINSIZE=16) The program is available to EMAS/IBM PC users from the ERCC Service Support Group, as an external command file (.EXE), but the user must supply his own disks. The default arrangement is for communications on COM1 port, parallel printer port LPT1, and a communications rate of 2400 Baud. Facilities exist within the program to temporarily reset the options for particular sessions. Program Overview : The program provides several facilities, the principal one being to enable the IBM PC to operate as an EMAS terminal. EMAS files may be listed to a parallel printer attached to the IBM PC , if desired, without being retained on the IBM PC storage system. The program also permits the transmission of files between EMAS and the IBM PC disks, in either direction. The cable connection between the serial port of the IBM PC and the EMAS TCP must be approved (and can be supplied) by the ERCC Service Support Group. Setting Up The Communications Link : 1. Connect serial output port COM1 to the TCP port by means of an ERCC approved cable. 2. Boot the IBM PC DOS Version 2.00 operating system. 3. Load a disk containing the external command module XTALK.EXE and give the instruction: XTALK 4. The program will clear the screen and display a heading, then wait for user action. 5. If it is desired to operate the system with a baud rate different to the default option, then type ^B to enter the temporary installation stage. (Hold down the Ctrl key, and press B at the same time). 6. If it is desired to establish network connection, press the space bar in the normal EMAS terminal log-on manner. 7. It is now possible to use EMAS or any other computer on the network. Information passing between the IBM PC user and the remote host, is buffered by the XTALK program before display on the IBM PC screen. If a parallel printer is attached to the IBM PC, then the information appearing on the screen may be 'slaved' to the printer. This may be achieved by typing ^P on the IBM PC, at the point printing is to commence. Printing may be terminated by a further ^P which will switch off printing immediately, but since most modern printers have a buffer printing may continue until drained. Because printers are normally slower than communication rates, it is possible to exceed the buffer capacity of XTALK (5K), if long printng outputs are requested. The user should limit this printing mode to small output requests and should wait, if possible, for the printer to catch up. For larger outputs the user should study the list facility provided by the XTALK program, where no such limitations apply. Temporary Installation Changes : It was explained earlier that there is a default arrangement for the serial port baud rate. This will normally be customised for a particular user when first obtaining the program. It is realised however, that situations may arise when a variation of this arrangement may be desired. The program provides for such eventualities and may be requested from the 'terminal emulation' mode of operation. This should normally be carried out prior to network attachement. Installation phase may be entered by typing ^B (holding down the Ctrl key, and pressing B at the same time). The program will respond with : S(et baud rate), Q(uit): Pressing the single letter Q will exit the user from the installation phase, back to 'terminal emulation' mode, and the user may then log-on to the network in the normal way. Any changes made during the installation phase will be effected when exit from the phase takes place. Pressing the single letter S will cause the program to respond with a prompt for Baud rate selection. Baud rate: A(300), B(600), C(1200), D(2400): The user should select the desired baud-rate by typing the relevant single letter reference. Although the prompt only indictaed baud rates up to 2400, which is the normal EMAS limit, the program will accept letters E and F for rates of 4800 and 9600 respectively. Transfer Of Files : It is sometimes desired that EMAS files be available on the IBM PC, or IBM PC files be available on EMAS. A link mode for bulk transfer of files may be established from the terminal emulation mode by typing ^L (hold down the Ctrl key and press L at the same time). The program will respond with the link mode menu. G(et), P(ut), L(ist), Q(uit link), B(inary), C(haracter), E(xit): Any of these facilities are effected by typing the relevant single letter reference. During the transfer of files, the information being transferred is not displayed but an asterisk is flashed on the screen whilst transfer is taking place. E(xit) The letter E will exit from link-mode back to the terminal emulation state, and EMAS will trigger the Command: prompt. Q(uit link) The letter Q will send the stop command to the remote host, to log-off, and exit from the XTALK program back to DOS. The user may log-off in the terminal emulation mode by typing STOP or QUIT in the normal way. If, however, it is desired to return to DOS, then it is still necessary to type ^L Q. If STOP is typed in the terminal emulation mode, then the user may log-on to another process or computer on the network, in the normal way, by pressing the space bar to start the procedure. B(inary), C(haracter) XTALK allows for files to be transferred in binary or in character mode. The need for alternatives is becuase EMAS does not store the 'return' character in character files. It is therefore necessary to either remove or insert a return character, depending on the direction of transfer, whenever a 'line-feed' is encountered. The removal and insertion of characters in true binary file transfer would, of course,be disasterous. C(haracter) type transfers are assumed by default. G(et) The letter G indicates that a file is to be transferred from EMAS to a disk on the IBM PC . XTALK will first request the name of the EMAS file which it is desired to transfer. This should be typed followed by a 'return' character. The program will then request the name of the EMAS file which it is desired to transfer. This should be typed followed by a 'return' character. The program will then reqeust the IBM PC filename, which should be given, preceded by the drive identifier (if not the currently selected) and include an extension, if desired. e.g. EMAS filename: ABCD IBM PC filename: B:SABCD.DAT Neither list of filenames must exceed the line length. P(ut) The letter P indicates that a file is to be transferred from the IBM PC to EMAS. The specification of filenames to be transferred is identical to that explained for G(et) above. L(ist) The letter L indicates that an EMAS file is to be printed (listed), on the printer attached to the IBM PC parallel port. Transfer is very similar to that described under G(et), except that only EMAS filenames are requested. The limitation on the quantity to be printed , which was indicated earlier, does not apply when the L(ist) operation is requested. There is no limit on the quantity to be printed. Information transferred under L(ist) and printed is not retained on the IBM PC or on its disks. N.B. Since the information to be printed is buffered into the IBM PC, printing will not take place until either the transfer buffer is full or the total file of information has been received. The program will not be able to cope with the following situations : a. Insufficient storage or index space on either system. b. Communication or computer failures. c. Operator messages from EMAS during transfer. (While transfer takes place all messages are suppressed) If there is a link breakdown, for any reason, between the IBM PC and EMAS while transfer is taking place, then the XTALK program may be left in a 'hang-up' state. In some circumstances the hang-up may be broken by typing a question mark (?), which is the terminator for bulk transfer to EMAS. On other occasions it may be necessary to re-boot DOS and re-enter XTALK. Control may then usually be regained by typing a 'return' or ESC A 'return'. If all efforts to recovery fail and the EMAS process is still running such that it is not possible to get back to Command level, then the last resort is to telephone the computer operator and ask for the process to be discontinued. The need for this drastic action should be rare.