feat(chibio): implement serial driver bindings for CHIBI/O

src/biosint.s

@@ -23,6 +23,28 @@ CHIBIO
   tfr d,x              ; Put in X for indexing mode
   jmp [CHIBIOPTRTBL,x] ; Jump!
 
-; Jump table TODO: Document function IDs and pointers
+; Jump table
 CHIBIOPTRTBL
-  fdb $8000 ; TODO Implement BIOS function wrappers (serial, etc)
+  fdb CIOPOUTCHAR ; serial/POUTCHAR wrapper
+  fdb CIOPOUTZSTR ; serial/POUTZSTR wrapper
+  fdb CIOPINCHAR  ; serial/CIOPINCHAR wrapper
+
+; POUTCHAR wrapper
+; @param B: char to write
+CIOPOUTCHAR
+  tfr b,a
+  jsr POUTCHAR
+  rti
+
+; POUTZSTR wrapper
+; @param X: start of zstring
+CIOPOUTZSTR
+  jsr POUTZSTR
+  rti
+
+; PINCHAR
+; @return A: filled with char from RX buffer or NUL if no char is ready
+; @return B: filled with LSR status codes masked with $9F
+CIOPINCHAR
+  jsr PINCHAR
+  rti