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README.md

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tu58em is a software emulation of a DECtapeII TU-58 block addressable cartridge tape drive. It requires only a standard Windows PC as a host with a (real or USB) RS232 serial comm port to connect to the target system.

tu58em was originally based on the 1984 Dan Ts'o tu58 program, but has been almost completely rewritten to make it compile error free, improve the program flow, and add new functionality. It has been compiled within the CYGWIN environment, and will run either within a CYGWIN window or an MSDOS command window with the associated cygwin1.dll helper file. tu58em has been tested under WinXPsp3, Win7sp1(64b), and Linux (Ubuntu 12.02LTS).

Each emulated .dsk image file is exactly 256KB (512 blocks of 512 bytes) of data and is a byte-for-byte image of the data on a TU-58 cartridge tape. As currently configured tu58em will support up to 8 drives per controller as DD0: to DD7: (altho this is easily changed in the source). tu58em will support disk image files as large as the TU58 protocol allows (ie, 32MB, or 64K 512B blocks); however most standard DEC operating system drivers restrict TU58 drives to 256KB each. The DEC driver must be patched to allow for larger than 256KB disk images.

As of v1.4m Mark Blair's updates for VAX mode operation (for VAX-730 microcode boot support) and background mode are integrated.

As of v2.0a the serial support routines have been rewritten to, under Linux, use termios.h PARMRK mode to allow detecting BREAK inline within the rx byte stream, and respond correctly (ie, abort current command in process and return to init loop). PARMRK mode in CYGWIN termios appears not be be working correctly at all. Windows communication mode (-DWINCOMM) is preferred for CYGWIN, as BREAK is detected correctly. MACOS support of PARMRK mode is unknown. The makefile is setup to detect the operating system type and define the compilation options correctly.

The following configurations have been tested:

System      Mode             Port           Status
----------  --------------   ------------   --------------------------------------
Win/CYGWIN  WINCOMM          real comm      PASS, BREAK detected
Win/CYGWIN  WINCOMM          USB ftdi       PASS, BREAK detected
Win/CYGWIN  WINCOMM          USB prolific   conditional PASS, BREAK not detected
----------  --------------   ------------   --------------------------------------
Win/CYGWIN  termios          real comm      conditional PASS; BREAK not detected
Win/CYGWIN  termios          USB ftdi       conditional PASS; BREAK not detected
Win/CYGWIN  termios          USB prolific   conditional PASS; BREAK not detected
----------  --------------   ------------   --------------------------------------
Win/CYGWIN  termios+PARMRK   any            FAIL, does not work at all
----------  --------------   ------------   --------------------------------------
Linux       termios+PARMRK   real comm      PASS, BREAK detected
Linux       termios+PARMRK   USB ftdi       PASS, BREAK detected
Linux       termios+PARMRK   USB prolific   conditional PASS; BREAK not detected
----------  --------------   ------------   --------------------------------------
Note:
(1) Win/CYGWIN = CYGWIN_NT-5.1 1.7.35(0.287/5/3) i686 Cygwin
(2) Linux = Ubuntu 12.04.5 LTS (GNU/Linux 3.2.0-124-generic) x86_64 GNU/Linux

So it appears that the drivers for real comm ports handle BREAK correctly, as does the driver for the USB ftdi adapter, on both WinXP and Linux. The USB prolific adapter hardware and/or driver do not handle a BREAK, altho all data transfers operate correctly.

A cygwin folder with a precompiled 32b cygwin executable (tu58em.exe) is included for those without cygwin environment access. Under Windows, just open a standard CMD.EXE window, change to the cygwin folder, and run the tu58em.exe executable as a command line program.

If the emulator is run with no options, it prints a usage screen:

E:\DEC> tu58em
ERROR: no units were specified
FATAL: illegal command line
  tu58 tape emulator v2.0a
  Usage: ./tu58em [-options] -[rwci] file1 ... -[rwci] file7
  Options: -V | --version            output version string
           -v | --verbose            enable verbose output to terminal
           -d | --debug              enable debug output to terminal
           -m | --mrsp               enable standard MRSP mode (byte-level handshake)
           -n | --nosync             disable sending INIT at initial startup
           -x | --vax                remove delays for aggressive timeout of VAX console
           -b | --background         run in background mode, no console I/O except errors
           -t | --timing 1           add timing delays to spoof diagnostic into passing
           -T | --timing 2           add timing delays to mimic a real TU58
           -s | --speed BAUD         set line speed to BAUD; default 9600
           -S | --stop BITS          set stop bits 1..2; default 1
           -p | --port PORT          set port to PORT [1..N or /dev/comN; default 1]
           -r | --read|rd FILENAME   readonly drive
           -w | --write FILENAME     read/write drive
           -c | --create FILENAME    create new r/w drive, zero tape
           -i | --initrt11 FILENAME  create new r/w drive, initialize RT11 directory
           -z | --initxxdp FILENAME  create new r/w drive, initialize XXDP directory
E:\DEC>

Most of the switches should be pretty obvious:

-V   prints the program version and exits
-v   sets verbose mode, which outputs status as the emulator runs
-d   sets debug mode, which dumps out all packets sent/received
-m   enables MRSP mode (VERY MUCH UNTESTED) instead of the default original RSP mode
-n   disables the sending of INIT characters at startup
-x   remove delays for aggressive timeout of VAX console
-b   run in background mode, no console I/O except errors
-t   adds time delays to allow the emulator to pass the DEC ZTUUF0 TU-58 Performance Exerciser diagnostic
-T   adds time delays to make the emulator nearly as slow as a real TU-58 (just for fun)
-s BAUD      sets the baud rate; the following rates may be supported. the default will be 9600 if not set.
                  3000000, 2500000, 2000000, 1500000, 1152000, 1000000, 921600, 576000, 500000,
                  460800, 230400, 115200, 57600, 38400, 19200, 9600, 4800, 2400, 1200
             exact list of baud rate support is system dependent (especially for rates above 230400)
-p PORT      sets the com port as a number (1,2,3,...) or if not numeric the full path (/dev/com1)
-S STOP      sets the number of stop bits (1 or 2), default is 1
-r FILENAME  set the next unit as a read only drive using file FILENAME
-w FILENAME  set the next unit as a read/write drive using file FILENAME
-c FILENAME  set the next unit as a read/write drive using file FILENAME, zero the file before use
-i FILENAME  set the next unit as a read/write drive using file FILENAME, initialize RT-11 filesystem before use
-z FILENAME  set the next unit as a read/write drive using file FILENAME, initialize XXDP filesystem before use

A sample run of tu58em, using COM3 at 38.4Kb, a read/only tape on DD0: using file boot.dsk, and a read/write tape on DD1: initialized with an RT-11 filesystem as file rt11.dsk:

E:\DEC> tu58em -p 3 -s 38400 -r boot.dsk -i rt11.dsk
info: initialize RT-11 directory on 'rt11.dsk'
info: unit 0 r    file 'boot.dsk'
info: unit 1 rwci file 'rt11.dsk'
info: serial port 3 at 38400 baud 1 stop
info: TU58 start
info: R restart, S toggle send init, V toggle verbose, D toggle debug, Q quit
info: TU58 emulator started
info: <BREAK> seen
info: <INIT><INIT> seen, sending <CONT>
info: read     unit=0 sw=0x00 mod=0x00 blk=0x0000 cnt=0x0400
info: read     unit=0 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
info: read     unit=0 sw=0x00 mod=0x00 blk=0x0001 cnt=0x0200
info: read     unit=0 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
info: read     unit=1 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
info: read     unit=1 sw=0x00 mod=0x00 blk=0x0001 cnt=0x0200
info: read     unit=1 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
info: write    unit=1 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
info: write    unit=1 sw=0x00 mod=0x00 blk=0x0001 cnt=0x0200
info: write    unit=1 sw=0x00 mod=0x00 blk=0x0000 cnt=0x0046
info: read     unit=0 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
info: write    unit=1 sw=0x00 mod=0x00 blk=0x0006 cnt=0x0400
  [ Q typed ]
info: TU58 emulation end
E:\DEC>