Tandy 1000 Technical Reference Manual

Tandy 1000
Technical Reference Manual
intel"
8272A
Table 1. Pin Description
Name and Function
Low Current/Direction:
Lowers Write current
on mner tracks in
Read/Wnte mode, de-
termines direction head
will step In Seek mode
Fault Reset/Step: Re-
sets fault FF In FDD In
Read/Write mode, pro-
Vides step pulses '0
move head to another
cylinder In Seek mode
D.C. Power: + 5V
Read Write / SEEK:
When "1" (high) Seek
mode selected and
when "0" (Iowl Read/
Write mode selected
FDD
f--- ---
FDD
34
---f------
36 0 FDD
35
37 0 FDD
40
38 0 FDD
39 0 FDD
Pin Connec-
No. Type tlon To
--
HDSEl
Head Load: Comnland
which causes read/write
head In FDD to contact
dISkette
---;-------+-::---:--------=--
Ready: Indicates FDD
is ready to send or re·
celve data. Must be tied
high (gated by the Index
pulse) for mini flOPpies
wh Ic h
do not normally
have a Ready line
--
Write Protect / Two-
Side: Senses Wrtle Pro-
tect status in Read/
Wnte mode. and Two
Side Media In Seek
mode
--------
Fault/Track 0: Sen>es
FDD fault condition In
Read Wnte mode and
Track 0 condition ,n
Seek mode
---+----+--+-----+---- ------
PS, PSo 31.32 0 FDD Precompensation (pre-
shift): Wnte precom-
pensation status dL;"ir:g
MFM mode, Determines
early, late. and norrnal
times
- .... 1---- --1-------
30 0 FDD Write Data: Senal c,ock
and data bits 10 FDD
--- t-------------
28.29 0 FDD Drive Select: Selects
FDD unit
--f----t--- -~---
27 0 FDD Head Select: Head 1
selected when 1
(high) Head 0 selected
when 0 (low)
DS,DS
o
'lvR
DATA
RDY
FR STP
~---+----+---- f-----
FLT TRKO 33 I FDD
---
HDl
Symbol
i------.----+--t--t-----ir--------------i
Vee
f------- -t----+----+-----;----------i
RWSEEK
1---- - --+-----+--
WP TS
Reset: Places FDC In
idle state Resets out·
put lines to FDD to "0"
(low). Does not clear the
last specify command
I'P
I' 'I I'P Read: Control Signal
for transfer of data from
FDC to Data Bus. when
o (low)
Data Bus: BidirectIOnal
8-Blt Data Bus
_._--
Data DMA Request:
DMA Reque~t IS being
made by FDC when
DRO 1
---
DMA Acknowledge:
DMA IS acTive
when (low) and
Controller IS perform-
Ing DMA Iransfer
--
FDD Index: Indicates the
beginning of a disk
track
-_.. ---
o I'P Interrupt: Interrupt Re-
quest Generated by
FDC
f--- ---- Clock: Single Phase 8
MHz (4 MHz fOl mini
flOPPies) Squarewave
__ Clg,,-k
Ground: DC Power
Return
DMA Terminal Count: Indl
cates the termination of
8. DMA transfer when
1 (hlgh}i'
Symbol
RD
CS
RESET
TC 16
r-----,----,--,------ - ,--------
Pin Connec-
No. Type tlon To Name and Function
f------------
IDX 17
f------- --
INT 18
f----
ClK
19
I-
GND 20
Note'
NOle 2
- -t--- +-----r----------
3 li" I'P Write: Control s,gnal
for transfer of data 10
FDC via Data Bus. when
o (low)
f---------+---- - -- r--------------
4 I ~ P Chip Select: IC selected
when 0 (low) allow
Ing AD and WR to be
enabled
.- --
I'P Data/Status Register
Select: Selects Data
Reg (AD = 1) or Status
Reg (A
o
= 0) contenlS
to be sent to Data Bus
DBa-DB,
6--13
10"
~P
e------
DRO
14
0
DMA
f-----
- --- ---
DACK
15 I
DMA
6-225
AFN·01259C

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