Wd1770 Fdc - Commodore Computers 1581 Service Manual

1581 SERVICE MANUAL
WD1770 FLOPPY DISK CONTROLLER
cs-
R/W-
A0-
A1-
DALO-
DAL1-
DAL2-
DAL3-
DAL4-
DAL5-
DAL6-
DAL7-
MR-
GND-
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
-INTRQ
-DRQ
-DDEN
-WPRT
-IP
-TR00
-WD
-WG
-MO
-RD
-CLK
-DIRC
-STEP
-vcc
1
2
3,4
CS
R/W
A0,A1
CHIP SELECT
READ/WRITE
ADDRESS 0,1
5-12 DALO- DATA ACCESS
DAL7 LINES 0 THRU 7
13 MR MASTER RESET
14 GND GROUND
15 Vcc POWER SUPPLY
16 STEP STEP
17 DIRC DIRECTION
18 CLK CLOCK
19 RD READ DATA
20 MO MOTOR ON
21 WG WRITE GATE
22 WD WRITE DATA
23 TROO TRACKOO
24 IP INDEX PULSE
25 WPRT WRITE PROTECT
26 DDEN DOUBLE DENSITY
ENABLE
27 DRQ DATA REQUEST
28 INTRQ INTERRUPT
REQUEST
CS
0
0
0
0
A1
0
0
1
1
AO R/W = 1
0 Status Reg
1 Track Reg
0 Sector Reg
1 Data Reg
A logic low on this input selects the chip and enable Host communication with the
device.
A logic high on this input controls the placement of data on the D0-D7 lines from
a selected register, while a logic low causes a write operation to a selected register.
These two inputs select a register to Read/Write data:
R/w = 0
Command Reg
Track Reg
Sector Reg
Data Reg
Eight bit bidirectional bus used for transfer of data, control, or status. This bus is
enabled by CS and R/W. Each line will drive one TTL load.
A logic low pulse on this line resets the device and initializes the status register (in
ternal pull-up).
Ground.
+ 5V ±5% power supply input.
The Step output contains a pulse for each step of the drive's RW head. The WD1770
and WD1772 offer different step rates.
The Direction output is high when stepping in towards the center of the diskette,
and low when stepping out.
This input requires a free-running 50% duty cycle clock (for internal timing) at 8 MHZ
±1%.
This active low input is the raw data line containing both clock and data pulses from
the drive.
Active high output used to enable the spindle motor prior to read, write or stepping
operations.
This output is made valid prior to writing on the diskette.
FM or MFM clock and data pulses are placed on this line to be written on the diskette.
This active low input informs the WD1770 that the drive's R/W heads are position
ed over Track zero (internal pull-up).
This active low input informs the WD1 770 when the physical index hole has been
encountered on the diskette (internal pull-up).
This input is sampled whenever a Write Command is received. A logic low on this
line will prevent any Write Command from executing (internal pull-up).
This input pin selects either single (FM) or double (MFM) density. When DDEN = 0,
double density is selected (internal pull-up).
This Active high output indicates that the data register is full (on a READ) or empty
(on a Write operation).
This Active high output is set at the completion of any command or reset or read
of the status register.
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