Fig. 9 - Floppy disk interface block diagram
In order to reduce the symbol crossover interference at write operations,
a circuit made with
U18
,
U12
is used, that ensures precompensation for data to
be written.
Gates
U16
,
U03
,
U06
,
U10
take care of multiplexing and level translation
for command signals of the floppy drives.
Gates
U16
,
U15
,
U14/6
,
U14/8
and counter
U08
generate the write clock
signal
WCK
and clock signal
CK
depending on the selected simple or double
(
MFM
) density.
Circuits
U13
,
U07
,
U14/12
,
U09
make up a phase locked loop circuit
(digital
PLL
) that is used to synthesize the data window
RDW
signal (Read Data
Window) starting from the transitions of data received from the selected floppy
drive. If input
U07/13
is in “1” logic level,
U13
along with
U07
make up a regular
divider-by-16 circuit. The positive edge of the
USD
signal from the floppy drive
18
Summary of Contents for CoBra
Page 20: ...Fig 10 Keyboard schematic 20 ...
Page 21: ...Fig 11 Keyboard schematic 21 ...
Page 23: ...Fig 13 Power source schematic 23 ...
Page 39: ...9 APPENDIX 1 CoBra Microcomputer Schematics 39 ...
Page 40: ...Fig A1 1 CoBra Microcomputer Central Processing Unit 40 ...
Page 41: ...Fig A1 2 CoBra Microcomputer Configurator and Selector Circuit 41 ...
Page 42: ...Fig A1 3 CoBra Microcomputer Read Only Memory Circuit 42 ...
Page 43: ...Fig A1 4 CoBra Microcomputer DRAM Memory Circuit 43 ...
Page 44: ...Fig A1 5 CoBra Microcomputer Memory Access Prioritizer and Command Logic 44 ...
Page 45: ...Fig A1 6 CoBra Microcomputer Video Address Generator Circuit 45 ...
Page 46: ...Fig A1 7 CoBra Microcomputer Video Address Multiplexer Circuit 46 ...
Page 47: ...Fig A1 8 CoBra Microcomputer Video Memory Circuit 47 ...
Page 48: ...Fig A1 9 CoBra Microcomputer Video Sync Pulses Generator Circuit 48 ...
Page 49: ...Fig A1 10 CoBra Microcomputer Video Signal Shape Generator 49 ...
Page 50: ...Fig A1 11 CoBra Microcomputer Interfaces 50 ...
Page 51: ...Fig A1 12 CoBra Microcomputer Voltage Level Adapter Circuits 51 ...
Page 52: ...Fig A1 13 CoBra Microcomputer Keyboard Interfacing Circuit 52 ...
Page 53: ...Fig A1 14 CoBra Microcomputer TV Monitor Interfacing Circuit 53 ...
Page 55: ...10 APPENDIX 2 Flopppy Disk Interface Schematics 55 ...
Page 56: ...Fig A2 1 Floppy Disk Interface Disk Controller 56 ...
Page 57: ...Fig A2 2 Floppy Disk Interface Command and Control Signals Generator Circuits 57 ...
Page 58: ...Fig A2 3 Floppy Disk Interface Write Clock and Digital PLL Circuits 58 ...
Page 59: ...10 APPENDIX 3 Component Placement on Boards 59 ...
Page 60: ...60 Fig A3 1 Component Placement on Keyboard Circuit Board ...
Page 61: ...61 Fig A3 3 Keyboard Circuit Board top layer seen from above keys side ...
Page 62: ...62 Fig A3 3 Keyboard Circuit Board bottom layer seen from above keys side ...
Page 63: ...Fig A3 5 Component placement on the floppy interface board 63 ...
