Worked around initConnection() failures due to machines that initialize more slowly, by also allowing each machine to invoke the other's initConnection(); if it turns out to be unnecessary, it's simply ignored

_posts/2016-08-19-connecting-an-ibm-pc-to-a-dec-vt100-terminal.md

@@ -0,0 +1,85 @@
+---
+layout: post
+title: Connecting an IBM PC to a DEC VT100 Terminal
+date: 2016-08-19 10:00:00
+permalink: /blog/2016/08/19/
+machines:
+  - id: ibm5170
+    type: pcx86
+    connection: com2->vt100.serialPort
+    config: /devices/pcx86/machine/5170/ega/2048kb/rev3/machine.xml
+  - id: vt100
+    type: pc8080
+    connection: serialPort->ibm5170.com2
+    config: /devices/pc8080/machine/vt100/machine.xml
+---
+
+Now that you've had a chance to play with a standalone [VT100 Terminal](/devices/pc8080/machine/vt100/), not to mention
+[Dual VT100 Terminals](/devices/pc8080/machine/vt100/dual/), it's time to take [PCjs Machines](/) to the next level, and
+begin connecting PCs to terminals.
+
+Below you'll find an 80286-based [IBM PC AT](/devices/pcx86/machine/5170/ega/2048kb/rev3/) connected to an 8080-based
+[VT100 Terminal](/devices/pc8080/machine/vt100/) via the PC's **COM2** serial port.
+
+At this point, the connection is *very* thin.  The [PCx86](/modules/pcx86/) [SerialPort](/modules/pcx86/lib/serialport.js)
+and [PC8080](/modules/pc8080/) [SerialPort](/modules/pc8080/lib/serialport.js) each export exactly two methods:
+
+- *initConnection()*
+- *receiveData()*
+
+The *receiveData()* method always returns *success*, because both SerialPort components buffer all received data.
+For now, the VT100 SerialPort component avoids overflowing the VT100 firmware's buffers by automatically throttling the flow
+of data whenever the firmware, in desperation, issues an XOFF.  This "Auto XOFF" behavior will eventually be superseded by
+additional interfaces that provide conventional RS-232 signal-based flow control.
+
+What can you do with these machines?  Click on the PC screen and type:
+
+	DIR > COM2
+
+or any command redirected to COM2.  The output should appear on the VT100's screen.
+
+A more interesting example:
+
+	CTTY COM2
+
+redirects all *stdout* (screen) and *stdin* (keyboard) I/O to the VT100.  Then click on the VT100 screen to switch focus,
+and you can now interact with the PC via the terminal.  The `CTTY CON` command will restore control to the PC.
+
+More useful scenarios include machines running PC-based debuggers that communicate via a serial port, such as the
+OS/2 kernel debugger, Windows debuggers like `WDEB386`, some versions of `SYMDEB`, and so on.  PC-to-PC configurations will
+also be possible, enabling live demonstrations of classic communication software packages such as `CROSSTALK`.
+
+I've also made it incredibly easy to put machines like this on any PCjs web page.  For this blog post, all I had to do
+was add the following Front Matter to the top of the Markdown file:
+
+	machines:
+	  - id: ibm5170
+	    type: pcx86
+	    connection: com2->vt100.serialPort
+	    config: /devices/pcx86/machine/5170/ega/2048kb/rev3/machine.xml
+	  - id: vt100
+	    type: pc8080
+	    connection: serialPort->ibm5170.com2
+	    config: /devices/pc8080/machine/vt100/machine.xml
+
+and then embed the machines in the post, each with a single line:
+
+	{% raw %}
+	{% include machine.html id="ibm5170" %}
+	{% include machine.html id="vt100" %}
+	{% endraw %}
+
+For people rolling their own web pages, [the basics](/docs/pcx86/) haven't changed, and adding a serial connection merely
+requires adding a *connection* property (eg, `connection:"com2->vt100.serialPort"`) to the *parms* parameter passed to the
+*embedPCx86()* interface.  A similar property (eg, `connection:"serialPort->ibm5170.com2"`) must also be added to the *parms*
+passed to *embedPC8080()*.
+
+For the more adventurous, a [Dual Debugger Configuration](/devices/pcx86/machine/5170/ega/2048kb/rev3/debugger/vt100/)
+is also available.
+
+{% include machine.html id="ibm5170" %}
+
+{% include machine.html id="vt100" %}
+
+*[@jeffpar](http://twitter.com/jeffpar)*  
+*Aug 19, 2016*