
  Firmware v0.41 11/23/10 for the HP21xx USB Disk Adapter
  =======================================================
  
Version 0.32 of the firmware was OK but slow, this new version should
be considerably faster (but maybe riskier).

Enhancements for 0.4 include...

"Fast" VDsend, VDreceive, VDsendWait, VDreceiveWait and VDclear subs
Better error detection in DeleteFile and FillReadBuffer subs
Modified "dos prompt" to (maybe) permit better binary control (not tested)
Moved some flag clocks to allow for better multitasking, lets HP move on
Increased read buffer size to 1536 bytes, write buffer to 1280 bytes
Punch data now shows on data LED's
Updated documentation.

There are a couple of CLEAR_MS settings near the top, these control
how long the VDclear sub waits for new data to appear, if any trouble
increase. The setting for QUADCLOCK 1 is the one enabled, delay is
1/4 the milliseconds listed due to the 32mhz clock. Note.. the code
has not been tested at all with QUADCLOCK 0, the only reason not to
run the chip at 32mhz would be for really sloppy wiring that won't
permit running at full SPI buss speed.

Fixes for 0.41...

Sending an empty filename to close a read file works now.
(only use to close a read file, use the close command to close a
 write file to ensure the data is actually written to disk)

For 0.41 also added a CLEAR_VDOS setting to control how long the
clear command waits when called as a command - some VDOS words don't
wait for data and will fail with the short setting used for CLEAR_MS.
Set to 25ms, which should be plenty but if issues increase the setting.

This is experimental software, there may be undiscovered problems.

Testing status...
Boots a ~40KB ABS HPBOOT file using the HP loader in about 3 seconds.
VDOS seems to work, overwrite detection seems to be OK (timing sensitive).
Saves and loads ABS files, VCOPY works, navigating, prompt, etc work.
Punch emulation works, mixing VDOS and PT emulation can be made to work,
used VDOS to load the vintage EXTASMB assembler, attach in/out files,
switch to PT mode using a CLA OTA 12 word, assembled the HP-IPL/OS kernel.
Used "vintage.ipl" package to compile/assemble/link FORTRAN/ALGOL/ASMB code.

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USB Disk Adapter page: http://newton.freehostia.com/hp/usbadapter.html
Terry Newton (wtn90125@yahoo.com)
