rc2014: add sio recipe

recipes/rc2014/README.md

@@ -27,6 +27,7 @@ are other recipes related to the RC2014:
 * [Accessing a MicroSD card](sdcard.md)
 * [Self-hosting](selfhost.md)
 * [Interfacing a PS/2 keyboard](ps2.md)
+* [Using Zilog's SIO as a console](sio.md)
 
 ## Recipe
 

recipes/rc2014/sio.md

@@ -0,0 +1,35 @@
+# Using Zilog's SIO as a console
+
+The RC2014 has an optional module called the Dual Serial Module SIO/2 which is
+built around Zilog's SIO chip. This module is nice because when paired with the
+Dual Clock Module and when using port B, it's possible to run a UART with a baud
+rate lower than 115200.
+
+Collapse OS has a driver for it (although for now, only port A is supported by
+it). Let's use it.
+
+## Gathering parts
+
+* A "classic" RC2014
+* A Dual Serial Module SIO/2
+
+## Build the binary
+
+You'll have to edit the base recipe's xcomp unit like we do in the sdcard
+recipe.
+
+* Locate RC2014 recipe in blkfs
+* Locate SIO driver
+* The driver main page gives you references for declarations and for code.
+* In the base xcomp unit, replace ACIA declataions with SIO's
+* Replace ACIA code with SIO's
+* At the bottom, replace "ACIA$" with "SIO$".
+
+You can build with `make`.
+
+## Setup
+
+After you've placed the binary on your RC2014's EEPROM, simply replace your
+regular Serial Module with the Dual Serial Module and plug yourself into port A.
+
+You should have a functional console.