[sebhc] 64K memory

[Walter Moore]

>From what I saw, it is not interchangeable with SCSI, not even close.
Did these definitions come from the Remex manual or from some variation
Heath made?  I Have the Remex service manual for the 4810 and 4820, which
also has all this information and much more.  I might get this scanned some
day if there is any interest.

I've taken a quick glance at the PC's parallel port, and I haven't decided
if it would be easy to emulate the Remex drive or not.  One of the problems
is that the Remex drive really wants to control the bus, just as the PC
does.  Another problem is that the Remex drive wants active LOW while the PC
wants active HIGH for the same signals.  I still need to figure this out.

..walt

-----Original Message-----
From: sebhc at sebhc.org [mailto:sebhc at sebhc.org] On Behalf Of Lee Hart
Sent: Sunday, May 16, 2004 11:25 PM
To: sebhc at sebhc.org
Subject: Re: [sebhc] 64K memory

Carroll Waddell wrote:
>
> I hadn't thought about that. If we could find out the commands for the
> H47, might be able to swing it. I've heard that the 47 interface was
> serial with all the smarts in the 47 drive.

No; it is an 8-bit parallel interface with handshaking -- much like
SCSI. In fact, I think the two are (nearly) interchangeable.

I have the Heath H47 documentation. I can copy it if anyone needs it.
Briefly, the States are:

- Master Reset mode
	computer sets /MRST line low
	H47 unconditionally ends all operations and enters Ready state
- Ready mode
	/BUSY line high, /DTR line low, /DDOUT line high, and the
	/ERROR line indicates H47's status. When the computer sets
	the /DTAK line, the H47 will read the data bus, clear the
	/DTR line, exit the Ready mode and attempt to execute the
	given command.
- Bootstrap command
	computer sends command word 0000h
	H47 sends 2 sectors of data bytes (one byte at a time)
	from unit 0, track 0, side 0, sectors 0 and 1
- Read Main Status command
	computer sends command word 0001h
	H47 sends its ERROR status byte
- Read Auxilary Status command
	computer sends command word 0002h, and side/unit/sector
	number on the bus.
	H47 sends its Auxiliary status byte, and sets the next
	side/unit/sector number to be read/written.
- Load Sector Count command
	computer sends command word 0003h, and number of sectors
	to be transferred
- Read Last Track/Side/Unit/Sector command
	computer sends command word 0004h
	H47 sends the last accessed track/side/unit/sector number
- Read Unbuffered Data command
	computer sends 0005h, track# byte, and side/unit/sector byte.
	H47 finds the requested data and transfers it to the computer,
	without buffering it (i.e. each byte is sent as it is found,
	about 1 every 16usec for a double-density disk).
- Read Buffered Data command
	computer sends 0007h, track# byte, and side/unit/sector byte.
	H47 finds the requested data and transfers it to the computer,
	buffering it in the H47's RAM (i.e. bytes can be received at
	any speed the computer can handle).
- Write Unbuffered Data command
	computer sends 0006h, track# byte, and side/unit/sector byte.
	H47 finds the requested sector, and writes the data to it,
	using a sector data mark of FBh. Data is transferred without
	buffering; the computer must be able to transfer a data byte
	every 16usec for a double-density disk.
    or	computer sends 0009h, track# byte, and side/unit/sector byte.
	H47 writes as for 0006h, but using sector data mark of F8h.
- Write Buffered Data command
	computer sends 0008h, track# byte, and side/unit/sector byte.
	H47 finds the requested sector, and writes the data to it,
	using a sector data mark of FBh. Data is transferred via the
	H47's RAM buffer, so the computer can transfer at any speed.
    or	computer sends 000Ah, track# byte, and side/unit/sector byte.
	H47 writes as for 0006h, but using sector data mark of F8h.
- Copy command
	computer sends 000Bh, track# byte and side/unit/sector byte
	for the start of the source data, and the track# and
	side/unit/sector byte for the destination.
	H47 copies sectors from source to destination until the
	number of sectors specified in the last Load Sector Count
	command is reached.
- Format command
	computer sends 000Ch, 000Dh, 000Eh, or 000Fh (selects density
	and sector size), then a byte defining the number of sectors
	per track, unit#, and side#.
	H47 formats the specified side/unit with the specified format.

There's lots more about the individual bit assignments etc. but this
should give you the general idea. This is a pretty high-level format,
with very little that needs to be done by the H8/H89 itself.
--
"Never doubt that a small group of committed people can change the
world. Indeed, it's the only thing that ever has!" -- Margaret Meade
--
Lee A. Hart  814 8th Ave N  Sartell MN 56377  leeahart_at_earthlink.net

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