Changes between Initial Version and Version 1 of CPC-CompactFlash

Timestamp:

May 19, 2014, 10:22:03 PM (10 years ago)

Author:

pulkomandy

Comment:

--

CPC-CompactFlash

@@ +1 @@
+= CPC-CompactFlash =
+
+This very simple interface (only 2 74LSxx chips) allows the use of a CompactFlash memory card on the CPC. It uses the 8 bit mode of the compact flash, making it even simpler than the IDE interfaces you can find elsewhere.
+
+== Schematics ==
+
+http://www.circuitbee.com/circuit/view/0000000374
+
+Also available (with PCB routing) in the SVN repository.
+
+== Programming information ==
+
+The interface maps the registers at addresses FEF0-FEFF :
+
+|Address|Read|Wrire|
+|FEF0|Data|Data|
+|FEF1|Error|Feature|
+|FEF2|Sector count|Sector count|
+|FEF3|LBA 0|LBA 0|
+|FEF4|LBA 1|LBA 1|
+|FEF5|LBA 2|LBA 2|
+|FEF6|Drive/LBA 3|Drive/LBA 3|
+|FEF7|Status|Command|
+
+Sector are accessed using 28-bit sector numbers in registers FEF3-FEF6. Only the 4 low bits of FEF6 are used, the 4 high bits must be set to E to enable LBA mode on the master drive.
+
+=== Initializing ===
+
+First of all, set the compact flash card to 8-bit mode:
+
+{{{
+        OUT &FEF6,&E0 ' Select master drive in LBA mode
+        OUT &FEF2,1 ' Sector count = 1
+        OUT &FEF3,0 ' Select first sector on drive
+        OUT &FEF4,0
+        OUT &FEF5,0
+
+        OUT &FEF1,1 ' 8bit mode feature code
+        OUT &FEF7,&EF ' execute SET FEATURE command
+}}}
+
+You can then identify the card:
+
+{{{
+        OUT &FEF6,&E0 ' Select master drive in LBA mode
+        OUT &FEF2,1 ' Sector count = 1
+        OUT &FEF3,0 ' Select first sector on drive
+        OUT &FEF4,0
+        OUT &FEF5,0
+
+        OUT &FEF7,&EC ' Send IDENTIFY command
+
+        ' Wait for the card to become ready to send data
+loop    A = IN &FEF7
+        IF A > &7F GOTO loop
+
+        ' Get the drive identification in IDENT array
+        FOR i = 0 to 512
+                IDENT(i) = IN &FEF0
+        NEXT i
+}}}
+
+The identification data is 512 bytes long and has information about the card (manufacturer id, model number, ...) and its capacity and format, and a few other less important things.
+
+You can also read sectors:
+
+{{{
+        OUT &FEF6,&E0 ' Select master drive in LBA mode
+        OUT &FEF2,1 ' Sector count = 1
+        OUT &FEF3,0 ' Select first sector on drive
+        OUT &FEF4,0
+        OUT &FEF5,0
+
+        OUT &FEF7,&20 ' Send READ SECTOR WITH RETRY command
+
+loop    A = IN &FEF7
+        IF A > &7F GOTO loop
+
+        ' Get the sector in DATA array
+        FOR i = 0 to 512
+                DATA(i) = IN &FEF0
+        NEXT i
+}}}
+
+== Using a filesystem ==
+
+Currently, no filesystem is available. Write one or wait for AmélieDOS to be released! Meanwhile, you can have fun with reading and writing sectors.