avrspi: first steps

After having done my initial handshaking, I thought the rest of the
job was only a matter of implementing the protocol, but I was wrong.
There were many issues to fix before I could reliably communicate
with my 328P, mostly timing.

Now, I seem to be able to reliably extract fuse information, but
only in batch mode (that is, run "asp$ aspfl@" directly, then
running "(spid)" before running the next command). If I try to
interact with the chip in a single asp$ session, I sometimes get
wrong values (but no sync error! that's worrying...).

blk/001

@@ -11,6 +11,6 @@ MASTER INDEX
 490 TRS-80 Recipe             520 Fonts
 550 TI-84+ Recipe             580 RC2014 Recipe
 600-619 unused                620 Sega Master System Recipe
-650 AVR assembler             690-729 unused
-730 8086 assembler
+650 AVR assembler             690 AVR SPI programmer
+700-729 unused                730 8086 assembler
 800 8086 boot code            830 PC/AT recipe

blk/690

@@ -0,0 +1,7 @@
+AVR SPI programmer
+
+This program allows you to access AVR chips Flash memory, EEPROM
+and fuses using a SPI relay. This requires drivers that imple-
+ment the SPI Relay protocol.
+
+Load range: B691-BXXX

blk/691

@@ -0,0 +1,14 @@
+: _cmd ( b4 b3 b2 b1 -- r4 )
+    (spix) DROP DUP (spix) DROP SWAP (spix) = ( b4 f )
+    SWAP (spix) SWAP ( r4 f ) NOT IF ABORT" AVR err" THEN ;
+: asp$ ( -- )
+    ( RESET pulse ) (spie) (spid) (spie)
+    ( wait 20ms ) 2000 0 DO LOOP
+    ( enable prog ) 0 0 0x53 0xac _cmd DROP ;
+: asprdy ( -- f ) 0 0 0 0xf0 _cmd NOT ;
+: aspfl@ ( -- lfuse ) 0 0 0 0x50 _cmd ;
+: aspfh@ ( -- hfuse ) 0 0 0x08 0x58 _cmd ;
+: aspfe@ ( -- efuse ) 0 0 0x00 0x58 _cmd ;
+: aspfl! ( lfuse -- ) 0 0xa0 0xac _cmd ;
+: aspfh! ( hfuse -- ) 0 0xa8 0xac _cmd ;
+: aspfe! ( efuse -- ) 0 0xa4 0xac _cmd ;