MWLyon
 
 
 

Design Work Completed

>Prototyping
 
>Schematic Capture
 
>PCB Layout
 
>Assembly Language Programming (8051)
 
>Firmware Programming
 
>Initial Fabrication

1995
Sync-Locked Timebase
 
z
VGADDS Board top side
 

VGADDS SPECIFICATIONS

This equipment is a VDR locked master pixel clock generator that replaces the VGA card master clock and allows v-locking the VGA display. It consists of a small board that is mounted to the VGA card. A Direct Digital Synthesis chip is used as the master clock source for the board. The DDS Chip can vary its frequency from 1 Hz to 20 Mhz in .01 Hz steps. This equipment also contains a microcontroller, EEPROM, and RS-232 I/O port. The uC configures the DDS chip, stores and recalls all the frequencies to/from the EEPROM, and communicates to a host computer via the RS-232 port. This unit contains 4 "video standard" registers. Each register contains a frequency, modified for that standard. These registers come stock containing:

STD 1 - 525/29.97

STD 2 - 625/25.00

STD 3 - 655/24.02

STD 4 - 655/24.00

The STD registers are modified through the use of a host computer via the RS-232 port and a series of commands to the microcontroller. The commands are as follows:

F ADJUSTS MASTER CLK FREQUENCY OF SELECTED STANDARD

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! MMSB MSB LSB LLSB THIS IS THE FREQ! 4 BYTES EXPECTED

? (MMSB MSB LSB LLSB) WHAT IS THE FREQ? 4 BYTES RETURNED

G GET uC FREQUENCY VALUES FROM EEPROM

P PUT uC FREQUENCY VALUES TO EEPROM

L LOAD uC FREQUENCY VALUES TO DDS

R RESTORE STOCK FREQUENCY VALUES

> COARSE INCREMENT FREQUENCY

< COARSE DECREMENT FREQUENCY

/|\ MEDIUM INCREMENT FREQUENCY (UP ARROW - 0Fh)

\|/ MEDIUM DECREMENT FREQUENCY (DN ARROW - 10h)

-> FINE INCREMENT FREQUENCY (RT ARROW - 0Eh)

<- FINE DECREMENT FREQUENCY (LT ARROW - 09h)

L LOAD uC FREQUENCY VALUES TO DDS

R RESTORE STOCK FREQUENCY VALUES

CR OUT AS IS NO EEPROM

ESC OUT AS IS NO EEPROM

 

VIDEO STANDARD SELECT

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S? (__) WHAT IS PRESENT STANDARD? 1 BYTE RETURNED

(ASCII 1, 2, 3 OR 4)

S1 SELECT STANDARD 1

S2 SELECT STANDARD 2

S3 SELECT STANDARD 3

S4 SELECT STANDARD 4

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SOFTWARE REBOOT

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ZR RESTART

ZZ INIT AND REBOOT SYSTEM

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All the above commands operate under the currently selected standard except S1 - S4, ZR, ZZ.

For instance, these commands will copy a frequency from one standard to another.

S1 SELECT STANDARD 1

F1 SELECT MASTER CLOCK DDS

G GET CURRENT FREQ FROM EEPROM INTO WORKSPACE

? (MMSB MSB LSB LLSB) WHAT IS THE FREQ? 4 BYTES RETURNED

CR BAIL LEAVING COPY OF FREQ IN WORKSPACE AND EEPROM UNCHANGED

S3 SELECT STANDARD 3

F1 SELECT MASTER CLOCK DDS

P PUT CURRENT FREQ FROM WORKSPACE INTO EEPROM

? (MMSB MSB LSB LLSB) WHAT IS THE FREQ? 4 BYTES RETURNED

CR BAIL LEAVING COPY OF FREQ IN WORKSPACE AND EEPROM CHANGED

These commands will adjust a frequency

S1 SELECT STANDARD 1

F1 SELECT MASTER CLOCK DDS

G GET CURRENT FREQ FROM EEPROM INTO WORKSPACE

Use the following to adjust the frequency using a freq. counter.

Outputting a string of the hex characters(i.e. holding down the arrow key) will continously Inc or Dec the freq.

/|\ COARSE INCREMENT PHASE (UP ARROW - 0Fh)

\|/ COARSE DECREMENT PHASE (DN ARROW - 10h)

> FINE INCREMENT PHASE (RT ARROW - 0Eh)

< FINE DECREMENT PHASE (LT ARROW - 09h)

P PUT CURRENT FREQ FROM WORKSPACE INTO EEPROM

CR BAIL LEAVING COPY OF FREQ IN WORKSPACE AND EEPROM CHANGED

 
z
VGADDS Board bottom side
 

 

 
 
 

 

 

 

  Copyright 1995-2019 by Michael W. Lyon: All rights Reserved