ATV_CALL_GENERATOR

Published:2009/7/15 4:41:00 Author:Jessie | From:SeekIC

Uses 32×SPROM togenerate up to six characters of amateur call Squares in matrix are numbered 1-32 horizontally and 1-8 vertically starting from upper left. and black squares forming call letters are programmed as 1s in PROM Pin connections shown for PROM are valid for AMI 27508/27509,82S23/82S123,MM5330/MM5331、HPROM 8256、and IM5600/5610. Two 7493 binary counters address all 32 words in ROM, with clock rate (2-3 MHz) determining length of characters on screen. 74151 multiplexer advances to next ROM output once per scan Line, under control of 7493 3-bit counter clocked by horizontal drive pulses from sync generator of ATV transmitter. Positive-going horizontal drive pulses reset 5-bit word counters, while positive-going vertical drive pulses reset 3-bit line counters, to make characters appear in same position on screen for all fields.-J. Pulice, Amateur Television Callsign Generator, Ham Padio, Feb. 1977, p 34-35.



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