Tandy 1000 Technical Reference Manual

Tandy 1000
Technical Reference Manual
inter
8272A
~M,.,~i;k- -·~~;",M-_M_-_
o 0
o I
---- ---- ._-
1 0
1 1
-------- -------
-1 -lif-
O 1
1
I
Table 7. Transfer Capacity
B~·tti;~;:~:~:~:~:~,~~~)F1~:~::~:~::~dl
01 (256)(26)== 6.656 or 26al Side 1
--- -----------------
00 112B)1521= 6,656
01 (256)(52)::= 13,312
- • --- - .- --- -- --------
01 (256)(15)= 3,840 15 af Side 0
---~~----t ::~:::::: :::: ---- or 15 al Side 1
02
(512)(30)= 15,360
-_ .. _--- ---------------
02 (512) (B) == 4,096 8 at Side 0
03 (1024) (8)
-= 8,192 or 8 at Side 1
------_ _----- -]
02 (512}(16)= 8,192
8 at Side '"
03 _ (1024)(16)= 16,384
1A
Sector 26al Side 0
OF Sector 15 at Side a
08 Sector 8 al Side a
Table 8. 10 Information When Processor
Terminates Command
lA Sector 1 to 25 at Side 1
OF Sector 1 to 14 al Side 1
08
Sector 1 to 7 at Side 1
1A Sector 26al Side 0
OF Sector 15 at Side 0
08
Sec lor 8 at Side a
Final Sector Tran.fe".ed 10
Proce,.or
EOT
lA Sector' lO 25 at Side 0
OF Sector 1 to 14 at Side 0
08 Sector 1 to 7 al Side 0
1A Sector 26al Side 1
OF Sector 15 at Side 1
08 Sector 8 al Side 1
lA Sector 11025 al Side 0
OF Sector 1 to 14 at Side 0
08 Sector' to 7 at Side 0
If the processor terminates a read (or write) operation in
the FDC, then the ID Information in the Result Phase IS
dependent upon the state of the MT bit and EaT byte.
Table 5
shows the values for C, H, R, and N, when the
processor terminates Ihe Command
During disk data transfers between the FDC and the
processor, via the data bus, the FDC must be serviced
by the processor every 27 IJS in the FM Mode, and every
13 IJS in the MFM Mode, or the FDC sets the OR (Over
Run) flag in
Status Register 1 to a I (high), and ter-
minates the Read Data Command,
The "multi-track" function (Mn allows the FDC to read
data from both sides of the diskette, For a particular
cylinder, data will be transferred starting at Sector 1,
Side 0 and completing at Sector L, Side 1 (Sector L = last
sector on the side), Note, this function pertains to only
one cylinder (the same track) on each side of the
diskette,
When N =0, then DTL defines the data length which the
FDC must treat as a sector. If DTL is smaller than the ac-
tual
data length in a Sector, the data beyond DTL in the
Sector is not sent to the Data Bus, The FDC reads (inter-
nally)
the complete Sector performing the CRC check,
and depending upon the manner of command termina-
tion, may
perform a Multi-Sector Read Operation, When
N
is non-zero, then DTL has no meaning and should be
set
to OFFH,
At the completion of the Read Data Command, the head
is
not unloaded until after Head Unload Time Interval
(specified in the Specify Command) has elapsed, If the
processor issues another command before the head
unloads then the head settling time may be saved be-
tween subsequent reads, This time out is particularly
valuable when a diskette is copied from one drive to
another
If the FDC detecls the Index Hole twice without finding
the right sector, (indicated in "R"), then the FDC sets
the ND (No Data) flag in Status Register 1 to a 1 (high),
and
terminates the Read Data Command, (Status
Register 0 also has bits 7 and 6 set to 0 and 1 respective-
ly,)
After reading the ID and Data Fields in each sector, the
FDC checks the CRC bytes, If a read error is detected
(incorrect CRC in ID field), the FDC sets the DE (Data Er-
ror) flag in Status Register I to a I '(high), and if a CRC er-
ror
occurs in the Data Field the FDC also sets the DD
(Data
Error in Data Field) flag in Status Register 2 to a I
(high), and terminates the Read Data Command, (Status
Register 0 also has bits 7 and 6 set to 0 and 1 respec-
tively,)
If the FDC reads a Deleted Data Address Mark off the
diskette, and the SK bit (bit D5 in the first Command
Word) is not set (SK = 0), then the FDC sets the CM (Con-
trol Mark) flag in Status Register 2 to a 1 (high), and ter-
minates the Read Data Command, after reading all the
data in the Sector. If SK = I, the FDC skips the sector
with the Deleted Data Address Mark and reads the next
sector.
Sector 11025 at Side 1
OF Sec lor 1 to 14 at Side 1
08
Sector1to7atSlde1
lA Sector 26 at Side 1
OF Sector 1Sal Side 1
08 Sector 8 at Side 1
NOles 1 NC (No Change\. The same value as the one at the beginning 01 command
e)(ecu!lon
Bill The least s'gnilicanl bit o~ H IS
WRITE DATA
A set of nine (9) bytes are required to set the FDC into
the Write Data mode. After the Write Data command has
been
issued the FDC loads the head (if it is in the
unloaded state), waits the specified head settling time
(defined in the Specify Command), and begins reading
ID
Fields, When the current sector number ("R"), stored
in the ID Register (IDR) compares with the sector
6-231

Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200