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TMXR, PDP11, PDP10, VAX: Add DDCMP sync framer support

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This adds support for the "framer" device, which is a USB-connected
device built around a Raspberry Pico that connects to a synchronous
line, either RS-232 or DEC "integral modem" coax connection.  It
implements the framing portion of DDCMP: clock recovery for the
integral modem case, byte sync, and DDCMP frame handling including
CRC.  The actual DDCMP protocol state machine, with its handling of
sequencing, timeout and retransmit, etc. is left to the host
software.  All the design files for the framer may be found at
https://github.com/pkoning2/ddcmp .

This commit adds code to drive the framer from the TMXR library,
allowing it to be used either from simulated DMC-11 or simulated
DUP-11 devices.  Both have been tested, using RSTS/E, RSX-11/M+, and
TOPS-20.

Fixed the one-digit limit on eth<n> device names, the limit is now 2.
This commit is contained in:
Paul Koning
2022-01-08 14:24:42 -08:00
committed by Mark Pizzolato
parent 030a47bdb4
commit 5cd1e8b7ac
9 changed files with 601 additions and 86 deletions
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# DDCMP synchronous line interface
The DDCMP synchronous interface supported by the DUP and DMC device emulations, is a USB connected device that implements synchronous links for use by DDCMP.
When used with SIMH, the synchronous interface allows an emulated DMC-11 or DUP-11 (including KMC/DUP) to be connected to a system that uses a real synchronous link for DDCMP, for example an actual DMC-11 device. The interface can support either RS-232 connectons for the DUP-11 or DMC-11 "remote" line cards, or the "integral modem" coaxial cable connection implemented in the DMC "local" line card. Speeds in the range 500 to 56k bits per second (for RS-232) or 56k to 1M bits per second (for integral modem) are supported.
The DDCMP synchronous line interface is an open source design. All the design files (schematics, circuit board layout, firmware, and documentation) may be found on GitHub at [this link](https://github.com/pkoning2/ddcmp "DDCMP Framer on GitHub").
Note that at the moment, no boards, kits, or assembled units are offered. If you want a framer, you would need to obtain a circuit board and assemble it. The documentation in the GitHub design files explains how to do this. The design uses all "through hole" parts, so modest electronics assembly skills suffice to build a unit.