Support for sticky machines when using the Node web server (so that we have parity between the Node and Jekyll web environments)

_posts/2017-01-03-pdp-11-tutorials.md

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+---
+layout: post
+title: PDP-11 Tutorials
+date: 2017-01-03 15:00:00
+permalink: /blog/2017/01/03/
+machines:
+  - id: test1170
+    type: pdp11
+    debugger: true
+    config: /devices/pdp11/machine/1170/vt100/debugger/machine.xml
+    connection: dl11->vt100.serialPort
+  - id: vt100
+    type: pc8080
+    config: /devices/pc8080/machine/vt100/machine.xml
+    connection: serialPort->test1170.dl11
+    sticky: top
+---
+
+Introducing PDP-11 tutorials! 
+
+{% include machine.html id="vt100" %}
+
+[PDPjs](/devices/pdp11/machine/) is the newest addition to the PCjs family of emulators, joining PCx86, PC8080, and C1Pjs.
+
+While PDPjs may eventually support a range of DEC PDP machines, my current focus is on the PDP-11, starting with the
+PDP-11/70.  From there, I'll work backwards to support other PDP-11 models, such as the PDP-11/45, until I reach the
+beginning of the PDP-11 line: the PDP-11/20.
+
+I'm starting with the top-of-the-line PDP-11/70 largely because the core of the emulator is being adapted from the
+JavaScript [PDP-11/70 Emulator (v1.3)](http://skn.noip.me/pdp11/pdp11.html) written by
+Paul Nankervis, who has generously given permission to use his code in PCjs.  Since his emulator is a fully functional
+11/70, it made sense to start there and work backwards, factoring out features as needed.
+
+The code has already undergone a lot of refactoring. Opcodes are now decoded by function tables rather than a single
+switch statement, and every opcode is implemented with a discrete function.  Other refactoring includes flag management,
+interrupt management, and device management.
+
+Most of the work remaining is in device management.  Like other PCjs emulators, PDPjs has a Bus component,
+[bus.js](/modules/pdp11/lib/bus.js), that allows separate device components to register I/O handlers for specific
+UNIBUS addresses.  During the initial port, I moved all of Paul's original device management code into one "catch-all"
+component, [device.js](/modules/pdp11/lib/device.js), which has now been converted to the new I/O registration model.
+
+The first new device component is [serial.js](/modules/pdp11/lib/serial.js), which is currently the
+only means PDPjs has of communicating with the outside world.  So you can try
+[PDPjs connected to a VT100 Terminal](/devices/pdp11/machine/1170/vt100/), by clicking the **Run** button on the test machine.
+The test machine is running [custom boot code](/apps/pdp11/boot/test/), adapted from boot code written by Paul, but due to the
+lack of other device support, nothing can be booted yet.
+
+Obviously PDPjs is very much a work-in-progress.  Before I proceed much farther, I really want to put the CPU through
+some rigorous testing, so I'll be on the lookout for some comprehensive PDP-11 instruction tests.  Or I'll write my own,
+and compare results across 1 or 2 other PDP-11 emulators.
+
+{% include machine.html id="test1170" %}
+
+*[@jeffpar](http://twitter.com/jeffpar)*  
+*Jan 3, 2017*