start-microcode regressfreq \ Reads 16-bit frequency from COMM, generates square \ wave at half frequency PIN2 : 1+ d# 1 + ; : @ dup c@ swap 1+ c@ swab or ; : ! over swab over 1+ c! c! ; : main d# 0 P2_DIR c! \ Make P2 an output \ Drive P2 high when raster is past line COMM+0 COMM+0 @ FREQHZ c! begin FREQTICK c@ P2_V c! again ; end-microcode