COMMENT ⊗   VALID 00006 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	ABSTRACT
C00004 00003	SPECIFICATIONS
C00005 00004	PRINCIPLES OF OPERATION
C00008 00005	IMPLEMENTATION
C00010 00006	CONTROL LINES
C00011 ENDMK
C⊗;
ABSTRACT

THE VIDEO INTENSITY TABLE IS A DEVICE WHICH WILL INTERFACE AND MODIFY
VIDEO INTENSITY INFORMATION BETWEEN THE DATA DISC CHANNELS AND A CRT
DISPLAY.  MODIFICATION OF THE VIDEO INTENSITY INFORMATION IS
NECESSARY TO HELP LINEARIZE THE SCALE WITH RESPECT TO THE BINARY
DATA. THAT IS, A BINARY VALUE (VIDEO INTENSITY) ONE HALF OF ITS MAX.
VALUE SHOULD PRODUCE A GRAY SHADE HALF WAY BETWEEN WHITE AND BLACK.
THIS MODIFICATION IS ACCOMPLISHED BY USE OF A RANDOM ACCESS MEMORY AS
A LOOK-UP TABLE.  THE BINARY VIDEO INTENSITY INFORMATION WILL BE USED
TO SPECIFY AN ADDRESS AND THE CONTENTS OF THAT ADDRESS WILL BE THE
MODIFIED VALUE OF THE VIDEO INTENSITY.  THE MEMORY WILL BE DIVIDED
INTO FOUR SUB-TABLES.  EACH OF THESE SUB- TABLES WILL BE LARGE ENOUGH
TO HANDLE THE FULL RANGE OF BINARY VALUES CONTAINING THE VIDEO
INTENSITY INFORMATION. THE TABLE SELECTION WILL BE CONTROLLED BY THE
PROCESSOR.  THE INITIAL LOADING OF THESE TABLES WILL ALSO BE DONE BY
THE PROCESSOR.  THE PROCESSOR WILL PROVIDE BOTH THE ADDRESS AND DATA
DURING MEMORY WRITE MODE.  IN READ MODE UNDER PROCESSOR CONTROL THE
TABLE CAN BE READ INTO THE PROCESSOR FOR VARIFICATION.
SPECIFICATIONS

	⊗  THE VIDEO INTENSITY DATA THROUGHPUT TIME WILL BE LESS
		THAN 100 nS.  THIS IS TO HANDLE THE DATA RATE OF
		10 MHZ FROM THE DATA DISC.

	⊗  THE STARTING ADDRESS FOR THE MAP WILL BE 171000.

	⊗  VIDEO INPUTS WILL BE TTL COMPATIBLE.

	⊗  BUSS INPUTS WILL BE UNIBUS COMPATIBLE.
	
	⊗  VIDEO OUTPUTS WILL DRIVE 50 OHM LINES.

PRINCIPLES OF OPERATION


DURING NORMAL OPERATION, THAT IS, WHEN IT IS BEING USED FOR VIDEO
INFORMATION PROCESSING, THE VIDEO INTENSITY INFORMATION COMING FROM
THE DATA DISC INTERFACE DRIVER BOARD ENTERS THE TABLE AND PASSES
THROUGH THE ADDRESS MULTIPLEXER.  THIS DATA USED AS AN ADDRESS
ACCESSES A WORD FROM MEMORY AND APPROX. 60 nS LATER THE CONTENTS OF
THAT WORD IS AVAILABLE AT THE INPUT OF THE OUTPUT LATCH.  AT THE END
OF THE 100 nS PERIOD A SHORT SYNC PULSE LATCHES THE OUTPUT BUFFER AND
THE DATA BECOMES AVAILABLE TO THE DAC.

THE MEMORY READ/WRITE OPERATION WILL BE COVERED NEXT.  TO THE
PDP-11/45 THE VIDEO INTENSITY TABLE LOOKS JUST LIKE MORE CORE MEMORY.
WHEN A `MOV' INSTRUCTION IS EXECUTED, THE DATA TO BE LOADED INTO THE
TABLE IS ON THE UNIBUS DATA LINES, THE ADDRESS FOR THAT PARTICULAR
WORD IS ON THE UNIBUS ADDRESS LINES AND THEN THE `MSYN' LINE IS
PULSED.  ADDRESSING ANY WORD ON THE VIDEO TABLE WILL CAUSE THE TABLE
TO GO TO READ/WRITE MODE.  SO DURING THE WHOLE EXECUTION CYCLE THE
TABLE WILL BE IN THIS MODE.  A SIMILAR STATEMENT CAN BE MADE FOR
READING DATA FROM THE TABLE.

WHEN THE TABLE IS IN READ/WRITE MODE THE ADDRESS IS CHANNELED THROUGH
THE ADDRESS MULTIPLEXER. THE DATA LINES ARE AT THE SAME TIME IS
CHANNELED TO EITHER THE DATA INPUT OR DATA OUTPUT LINES OF THE MEMORY
DEPENDING WHETHER THE 11 IS WRITING OR READING INTO THE TABLE. MEMORY
WRITE IS STROBED BY THE `MSYN' LINE.  THIS IS DONE TO GIVE SUFFICIENT
SETUP TIME FOR THE ADDRESS AND THE DATA.

IMPLEMENTATION

THE VIDEO INTENSITY TABLE IS BUILT ON A DEC 4-PADDLE BOARD USING 37
TTL ICs.  MOST OF THE INTEGRATED CIRCUITS ARE OF THE SCHOTTKY
VARIETY.  THE DEC BOARD ON WHICH THE DEVICE IS BUILT PLUGS INTO THE
LOWER FOUR SLOTS OF AN ACTIVE DD11 MODULE IN THE ELECTRONICS SUPPORT
CABINET.

COMMUNICATION TO THE OUTSIDE WORLD IS THROUGH 19 RG174 COAX CABLES.
eight OF THESE ARE FOR VIDEO INTENSITY INPUT, 10 ARE FOR VIDEO
INTENSITY OUTPUT. THE LAST REMAINING LINE IS THE SYNC PULSE.  THESE
LINES ARE DRIVEN WITH 50 OHM LINE DRIVERS (SN74128) AND ARE
TERMINATED.  THE CABLE ASSEMBLY CONSISTS OF THE 17 COAX CABLES
TERMINATED AT EACH END WITH A CONNECTOR BOARD.  ONE END OF THE CABLE
PLUGS INTO SLOT #2 (C,D) WITH THE ARROWS ON THE BOARD HANDLES
POINTING UP.  THE CONNECTOR/DRIVER CARD IS BUILT ON A VECTOR BOARD
WHICH PLUGS INTO THE VIDEO SYNTHESIZER RACK.

NOTE: THE DD11/B WHICH IS USED FOR THE VIDEO INTENSITY TABLE HAS BEEN
HACKED UPON.  USE THIS DD11/B AT YOUR OWN RISK.
CONTROL LINES

 
RANDOM ACCESS MEMORY - Write memory - ¬WRTMEM

BUS TRANSCEIVER - Write bus - ¬WRTBUS

ADDRESS SELECT -Video select - ¬VIDSEL


CONTROL LOGIC


A17 ∧ A16 ∧ A15 ∧ A14 ∧ A13 ∧ A12 ∧ ¬A11 ∧ ¬A10 → MAPSEL

vidsel ∧ BUS MSYN → BUS SSYN

BUS MSYN ∧ VIDSEL ∧ C1 → WRTMEM

bus msyn ∧ vidsel ∧ ¬c1 → wrtbus