--- a/defs/cocosdc.d	Sat Dec 20 12:52:07 2014 -0600
+++ b/defs/cocosdc.d	Mon Dec 22 21:06:37 2014 -0800
@@ -1,6 +1,3 @@
-          IFNE      COCOSDC.D-1
-COCOSDC.D SET       1
-
 ********************************************************************
 * cocosdc.d - CoCo SDC definitions
 *
@@ -11,8 +8,38 @@
 * ------------------------------------------------------------------
 *          2014/05/02  Boisy G. Pitre
 * Created
+*          2014/12/22  Darren Atkinson
+* Additional hardware symbols
+
+               IFNE      COCOSDC.D-1
+COCOSDC.D      SET       1
 
 
+* Main Port Address (V.PORT)
 SDAddr         SET       $FF4A
 
+* Hardware Addressing - CoCo Scheme
+CTRLATCH       equ       $FF40              controller latch (write)
+CMDREG         equ       $FF48              command register (write)
+STATREG        equ       $FF48              status register (read)
+PREG1          equ       $FF49              param register 1
+PREG2          equ       $FF4A              param register 2
+PREG3          equ       $FF4B              param register 3
+DATREGA        equ       PREG2              first data register
+DATREGB        equ       PREG3              second data register
+FLSHDAT        equ       $FF42              flash data register
+
+* Status Register Masks
+BUSY           equ       %00000001          set while a command is executing
+READY          equ       %00000010          set when ready for a data transfer
+FAILED         equ       %10000000          set on command failure
+
+* Command and Mode Values
+CMDMODE        equ       $43                control latch value to enable command mode
+CMDREAD        equ       $80                read logical sector
+CMDWRITE       equ       $A0                write logical sector
+CMDEX          equ       $C0                extended command
+CMDEXD         equ       $E0                extended command with data block
+
+
                ENDC