PAL20X10 PAL DESIGN SPECIFICATION P7051 BIRKNER/UDI 7/13/81 SCAN/LINE GENERATOR MMI SUNNYVALE, CALIFORNIA CK /CHAR5 /CHAR4 /CHAR3 /CHAR2 /INITS /H255 /WRITE /TSYNC /CHAR1 /CHAR0 GND /OC /LINE4 /LINE3 /SYNC /SCAN3 SCAN2 SCAN1 SCAN0 /LINE2 /LINE1 /LINE0 VCC /SCAN0 := INITS ;INITIALIZE + /INITS*/SCAN0 ;HOLD :+:/INITS*H255 ;INCREMENT /SCAN1 := INITS ;INITIALIZE + /INITS*/SCAN1 ;HOLD :+:/INITS*H255*SCAN0 ;INCREMENT /SCAN2 := INITS ;INITIALIZE + /INITS*/SCAN2 ;HOLD :+:/INITS*H255*SCAN0*SCAN1*/SCAN3 ;INC IN MODULUS 12 SCAN3 := /INITS*SCAN3 ;HOLD + /INITS*H255*LINE4*LINE2*LINE0 ;DETECT SCAN LINE 260 *SCAN2*SCAN1*SCAN0 ;FOR VERTICAL RETRACE :+:/INITS*H255*SCAN0*SCAN1*SCAN2 ;INCREMENT + /INITS*H255*SCAN3*SCAN1*SCAN0 ;MODULE 12 CORRECTION ;INITIAL WHEN INITS=H LINE0 := /INITS*LINE0 ;HOLD + /TSYNC ;TEST SYNC :+:/INITS*H255*SCAN3*SCAN1*SCAN0 ;INCREMENT + /INITS*H255*LINE4*LINE2*LINE0 ;DETECT LINE 21 7/12 *SCAN2*SCAN1*SCAN0 ;FOR VERTICAL RETRACE LINE1 := /INITS*LINE1 ;HOLD + /TSYNC ;TEST SYNC :+:/INITS*H255*SCAN3*SCAN1*SCAN0*LINE0 ;INCREMENT LINE2 := /INITS*LINE2 ;HOLD + /INITS*LINE2 ;EXTEND :+:/INITS*H255*SCAN3*SCAN1*SCAN0*LINE0*LINE1 ;INCREMENT + /INITS*H255*LINE4*LINE2*LINE0 ;DETECT LINE 21 7/12 *SCAN2*SCAN1*SCAN0 ;FOR VERTICAL RETRACE LINE3 := /INITS*LINE3 ;HOLD + /INITS*LINE3 ;EXTEND :+:/INITS*H255*SCAN3*SCAN1*SCAN0 ;INCREMENT *LINE2*LINE1*LINE0 LINE4 := /INITS*LINE4 ;HOLD + /TSYNC ;TEST SYNC :+:/INITS*H255*SCAN3*SCAN1*SCAN0 ;INCREMENT *LINE3*LINE2*LINE1*LINE0 + /INITS*H255*LINE4*LINE2*LINE0 ;DETECT LINE 21 7/12 *SCAN2*SCAN1*SCAN0 ;FOR VERTICAL RETRACE SYNC := CHAR5*CHAR4*/CHAR3*CHAR2*/WRITE ;CHAR 52-55 HORIZ SYNC + LINE0*LINE1*/LINE2*LINE4*/SCAN2*/SCAN3*SYNC;VERTICAL SYNC :+: LINE0*LINE1*/LINE2*LINE4*/SCAN2*/SCAN3*SYNC;WHEN LINE=19 SCAN 0-3 *CHAR5*CHAR4*/CHAR3*/CHAR2 ;AND CHAR 48-51 FUNCTION TABLE CK CHAR5 CHAR4 CHAR3 CHAR2 CHAR1 CHAR0 TSYNC INITS H255 WRITE /OC LINE4 LINE3 LINE2 LINE1 LINE0 SYNC SCAN3 SCAN2 SCAN1 SCAN0 ; T I W ; S N H R S ; Y I 2 I / Y ; C CHAR N T 5 T O LINE N SCAN ; K 543210 C S 5 E C 4321O C 321O COMMENTS ------------------------------------------------------------------------- C XXXXXX H H X X L LLLLL X LLLL INITIALIZE COUNTERS C XXXXXX H L H X L LLLLL X LLLH INC SCAN C XXXXXX H L H X L LLLLL X LLHL INC SYNC C XXXXXX H L H X L LLLLL X LLHH INC SYNC C XXXXXX H L H X L LLLLL X LHLL INC SCAN C XXXXXX H L H X L LLLLL X LHLH INC SCAN C XXXXXX H L H X L LLLLL X LHHL INC SCAN C XXXXXX H L H X L LLLLL X LHHH INC SCAN C XXXXXX H L H X L LLLLL X HLLL INC SCAN C XXXXXX H L H X L LLLLL X HLLH INC SCAN C XXXXXX H L H X L LLLLL X HLHL INC SCAN C XXXXXX H L H X L LLLLL X HLHH INC SCAN C XXXXXX H L H X L LLLLH X LLLL INC LINE, INC SCAN MODULE 12 C XXXXXX H L H X L LLLLH X LLLH LINE = 1, INC SCAN C XXXXXX H L H X L LLLLH X LLHL LINE = 1, INC SCAN C XXXXXX H L H X L LLLLH X LLHH LINE = 1, INC SCAN C XXXXXX H H X X L LLLLL X LLLL INITIALIZE COUNTERS C HHLLXX L L L X L HLLHH L LLLL LINE = 19, FOR TESTING VERTIC SYNC C HHLLXX H L H X L HLLHH L LLLH VERTICAL SYNC C HHLLXX H L H X L HLLHH L LLHL VERTICAL SYNC C HHLLXX H L H X L HLLHH L LLHH VERTICAL SYNC C HHLLXX H L H X L HLLHH L LHLL INC SCAN C HHLLXX H L H X L HLLHH L LHLH INC SCAN C HHLHXX H L L L L XXXXX H XXXX HORIZONTAL SYNC ----------------------------------------------------------------------------- DESCRIPTION EACH CHARACTER ON THE SCREEN CONSISTS OF 12 DOT LINES: 7 LINES FOR THE CHARACTER AND 5 LINES FOR SPACE BETWEEN CHARACTERS. THE FOLLOWING FIGURE SHOWS THE LETTER "U" AND THE SPACE WITH ALL THE PIXELS AROUND IT AS IT IS DISPLAYED BY THE VIDEO CONTROLLER. "SCAN" IS A MODULE 12 COUNTER THAT COUNTS THE NUMBER OF THE DOT LINES FOR EACH CHARACTER. "LINE" COUNTS THE NUMBER OF THE CHARACTER LINES. EACH CHARACTER LINE IS 12 SCAN LINES. THE COUNTER COUNTS UNTIL 21 ALTHOUGH ONLY 16 LINES ARE VISIBLE ON THE SCREEN. THE HORIZONTAL SYNC PULSES ARE GIVEN IN EVERY SCANNED LINE BETWEEN CHAR 52 AND 55. THE VERTICAL SYNC PULSE IS GIVEN WHEN THE LINE COUNT IS 19, SCAN IS BETWEEN 0 AND 3, AND CHAR IS BETWEEN 48 AND 51. THE NEXT FIGURE SHOWS THE SCREEN WITH THE CORRESPONDING LINE AND CHAR COUNTERS, AND THE SYNC PULSES.