CoCo: updated needed BIOS file

Author: cmitu

docs/Coco.md

@@ -6,7 +6,7 @@ _The Tandy Colour Computer series were home computers originally released by the
 
 | Emulator | Rom Folder | Extension | BIOS |  Controller Config |
 | :---: | :---: | :---: | :---: | :---: |
-| [XRoar](http://www.6809.org.uk/xroar/) | coco  | .cas .wav .bas .asc .dmk .jvc .os9 .dsk .vdk .rom .ccc .sna | bas13.rom | hardcoded |
+| [XRoar](http://www.6809.org.uk/xroar/) | coco  | .cas .wav .bas .asc .dmk .jvc .os9 .dsk .vdk .rom .ccc .sna | bas13.rom, extbas11.rom, coco3.rom, coco3p.rom | hardcoded |
 
 ## Emulator: [XRoar](http://www.6809.org.uk/xroar/)
 
@@ -19,9 +19,15 @@ Place your CoCo ROMs in
 ```
 ## BIOS
 
-The file needed is **bas13.rom**
+Depending on the emulated model, different BIOS files are need to be copied to
 
-Place your bas13.rom BIOS file in
 ```
 /home/pi/RetroPie/BIOS
-```
+```
+
+| Machine | BIOS file name | Size |
+| :- | :- | :- |
+| Tandy Colour BASIC	| bas13.rom |	8K |
+| Tandy Extended BASIC	| extbas11.rom |	8K |
+| Tandy Super ECB (CoCo 3)	| coco3.rom	32K | (32768 bytes) |
+| Tandy Super ECB (PAL CoCo 3) |	coco3p.rom	| 32K (32768 bytes) |