D6G
Sprow
999
SUBJECT - ANSWERS TO QUESTIONS
Printer Dump inverter
=====================
A couple of issues back Syd
Hetherington was having problems
printing out screen dumps that he had
scanned/digitised.
I can't remember whether I sent my
response - so here it is anyway.
Use VDU18,3,129,16
This will make the OS EOR all the
screen memory bytes with 255,
resulting in the whole screen being
swapped black for white.
This should result in your screen
dumper printing out properly.
An example use might be:
10MODE0
20*LOAD filename 3000
30VDU18,3,129,16
40*DUMPSCREEN (or whatever)
Hope this is of help in saving you ink!
Osword &7F
==========
Even further back in the myths of time
a puzzled member was in search of a
1770 equivalent to the "Advanced Disk
User Guide".
Well,I don't have one either,but I do
have a chart of how the new 1770
commands map onto the old.In general
Location Contents
---------------------------------------
BLOCK+0 DRIVE# (0-3 OR FF FOR SAME)
BLOCK+1 DATA ADDRESS LOW
BLOCK+2 DATA ADDRESS HIGH
BLOCK+3 HIGH ORDER (FF OR 00 IF I/O
ONLY)
BLOCK+4 AS PER BLOCK+3
BLOCK+5 NUMBER OF DETAILS (0-3)
BLOCK+6 COMMAND CODE (SEE BELOW)
BLOCK+7 1ST DETAIL (USUALLY TRACK#)
BLOCK+8 2ND DETAIL (USUALLY SECTOR#)
BLOCK+9 3RD DETAIL (USUALLY SECTOR
SIZE + NUMBER OF SECTORS
INVOLVED)
BLOCK+10 RESULT RETURNED HERE
The result code will appear earlier if
less details are supplied,ie.at block+8
if only 1 detail is reqd.
Command Code Details
---------------------------------------
Seek &69 Track#
Read status &6C None
Write spec reg &5A Reg#,data
Read spec reg &5D Reg#
Read sectors &53 Track,sector,# of
sectors to be read
Read deleted &5B Track,sector,# of
sectors to be read
Read ID &5B # of IDs
Verify sectors &5F Track,sector,# of
sectors to verify
Write sectors &4B Track,sector,# of
sectors to write
Format &4B Track,Gap3-6,size/
# of sector,Gap5-6
Gap1-6.
The seek command moves to head to the
specified place.
The status byte returned for read
status is returned in one byte,with
bits 0 and 7 set to zero.
D6 D5 D4 D3 D2 D1
RDY1 WRTFAULT INDEX WRTPROT RDY0 TRACK0
Anyone who buys the £30 1770 machine
off me can have the entire of this
manual - it's too much to type in!
FX3 - the full story
====================
I made a typo in the QUIDFIX program,
and last month suggested you try FX3,10
instead.
Someone wrote to me asking what this
meant in terms of bit patterns,well,
I'll send you the Acorn application
note on the subject if you want.
It can be emailed to you,or posted.See
the *CUSTOM section of my forsale list
for details about app notes.
Disk speeds
===========
John Robson (D8J) was experiencing
drive problems with a Master.Assuming
they were the same make of drive,with
the same option link settings inside
one can assume that it is the computer
at fault.
Using two different Masters to test
this on would lead me to think that
they had different drive controllers
in - early Masters had 1770's in, the
later issues (mine has) a 1772 in.
These interpret the FDRIVE
configurations slightly differently,
so even if both machines had the save
software setting the hardware may be
thinking otherwise.
They are:
Value Step time Precomp?
WD1770 WD1772
0 or 4 6ms 6ms yes
1 or 5 6ms 6ms no
2 or 6 30ms 3ms yes
3 or 7 30ms 3ms no
Most drives require 6ms step time.
Older drives may need the 30ms step
time; modern drives may be able to
operate at 3ms - consult your disc
drive documentation.
Factory default : 0
"Precomp?" indicates whether, when
using ADFS, precompensation will be
used.
The rest of this configuration
application note is available - see
*CUSTOM section for more details.
You also said they were cutting out,
this I attribute to a dry joint or
similar poor mechanical problem,such
as overheating or cracked track.
The relay that clicked randomnly for
you may well be a serial ULA problem
as this is what used to control it
on the BBC B.
If you're still having problems,
contact me and I can of course have
a look at it for you (see the
regular contacts section under Sprow
Cubed)
Magazines
=========
I myself don't know what happened to
The Micro User and Acorn Computing
but I've a feeling someone told me
and it went something like this:
BBC Micro user changed name to The
Micro user after the BBC moaned about
copyright.
In parallel with this Acorn Computing
mopped up any Archimedes stuff.When
interest in the BBC fell,the two
merged to form Acorn Computer User
which as a remarketing ploy (cf.
Snickers and Marathon) renamed
themselves as Acorn User.That brings
us right up to 1996.
Please do correct me if I've missed
anything out in this history.
Keep BBCing!
Robert Sprowson.