You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.

99 lines
4.4 KiB

  1. PAL20X8 PAL DESIGN SPECIFICATION
  2. VP5 BIRKNER/KAMZI/UDI 7/14/81
  3. COMPOSITE VIDEO/BAUD RATE GENERATOR
  4. MMI SUNNYVALE, CALIFORNIA
  5. CK /DOT4 /SYNC NC NC NC INT /WRITE /DTCNT0 /DTCNT1 /DTCNT2 GND
  6. /OC /SYNOUT /UEN /9600X8 /BAUD3 /BAUD2 /BAUD1 /BAUD0 NC NC VIDEO VCC
  7. IF( SYNC ) SYNOUT = SYNC ;SYNC PULSE
  8. IF( /DOT4 ) /VIDEO = /DOT4 ;PIXEL TO THE SCREEN
  9. 9600X8 := INT ;TO INITIALIZE COUNTER BAUD
  10. + BAUD3*BAUD2*DTCNT2*DTCNT1*/DTCNT0 ;104/8 = 13, MODULE 102
  11. ;COUNTS 103 = 12 6/8
  12. BAUD0 := /9600X8*BAUD0 ;HOLD
  13. + /9600X8*BAUD0 ;EXTEND
  14. :+: /9600X8*DTCNT2*DTCNT1*DTCNT0 ;INC
  15. BAUD1 := /9600X8*BAUD1 ;HOLD
  16. + /9600X8*BAUD1 ;EXTEND
  17. :+: /9600X8*DTCNT2*DTCNT1*DTCNT0*BAUD0 ;INC
  18. BAUD2 := /9600X8*BAUD2 ;HOLD
  19. + /9600X8*BAUD2 ;EXTEND
  20. :+: /9600X8*DTCNT2*DTCNT1*DTCNT0 ;INC
  21. *BAUD1*BAUD0
  22. BAUD3 := /9600X8*BAUD3 ;HOLD
  23. + /9600X8*BAUD3 ;EXTEND
  24. :+: /9600X8*DTCNT2*DTCNT1*DTCNT0 ;INC
  25. *BAUD2*BAUD1*BAUD0
  26. UEN := WRITE*/DTCNT2*DTCNT1 ;DTCNT = 2,3
  27. + WRITE* DTCNT2*/DTCNT1*/DTCNT0 ;DTCNT = 4
  28. FUNCTION TABLE
  29. CK DOT4 SYNC INT WRITE DTCNT2 DTCNT1 DTCNT0 /OC SYNOUT UEN
  30. 9600X8 BAUD3 BAUD2 BAUD1 BAUD0 VIDEO
  31. ; S 9
  32. ; W Y 6 V
  33. ; D S R N 0 I
  34. ; O Y I I / O U 0 D
  35. ; C T N N T DTCNT E U E X BAUD E
  36. ; K 4 C T E 210 N T N 8 3210 O COMMENTS
  37. ----------------------------------------------------------------------
  38. L X H X X XXX L H X X XXXX X CHECK SYNOUT FOR H
  39. L X L X X XXX L L X X XXXX X CHECK SYNOUT FOR L
  40. L L X X X XXX L X X X XXXX L VIDEO = L
  41. L H X X X XXX L X X X XXXX H VIDEO = B
  42. C X X H X LLL L X X H XXXX X SET 9600X8
  43. C X X L X LLL L X X L LLLL X INITIALIZE BAUD COUNTER
  44. C X X L X HHH L X X L LLLH X INC BAUD
  45. C X X L X HHH L X X L LLHL X INC BAUD
  46. C X X L X HHH L X X L LLHH X INC BAUD
  47. C X X L X HHH L X X L LHLL X INC BAUD
  48. C X X L X HLH L X X L LHLL X HOLD BAUD: DTCNT NEQ HHH
  49. C X X L X HHH L X X L LHLH X INC BAUD
  50. C X X L X HHH L X X L LHHL X INC BAUD
  51. C X X L X HHH L X X L LHHH X INC BAUD
  52. C X X L X HHH L X X L HLLL X INC BAUD
  53. C X X L X HHH L X X L HLLH X INC BAUD
  54. C X X L X HHH L X X L HLHL X INC BAUD
  55. C X X L X HHH L X X L HLHH X INC BAUD
  56. C X X L X HHH L X X L HHLL X INC BAUD
  57. C X X L H LLL L X L L HHLL X HOLD BAUD
  58. C X X L H LLH L X L L HHLL X HOLD BAUD
  59. C X X L H LHL L X H L HHLL X HOLD BAUD, SET UEN
  60. C X X L H LHH L X H L HHLL X HOLD BAUD, SET UEN
  61. C X X L H HLL L X H L HHLL X HOLD BAUD, SET UEN
  62. C X X L H HLH L X L L HHLL X HOLD BAUD
  63. C X X L H HHL L X L H HHLL X SET 9600X8, HOLD BAUD
  64. C X X L H HHH L X L L LLLL X INITIALIZE BAUD
  65. ----------------------------------------------------------------------
  66. DESCRIPTION
  67. THIS PAL GENERATES THE BAUD RATE, THE VIDEO AND THE SYNC SIGNALS WITH CARE
  68. COMBINED AT THE OUTPUTS TO FORM THE COMPOSITE VIDEO SIGNAL, AND THE "UEN"
  69. SIGNAL WICH ENABLE THE "URT".
  70. EVERY CHARACTER CONSISTS OF 10 BITS: 1 START BIT, 7 ASCII CODE BITS, 1
  71. PARITY BIT, AND 1 STOP BIT. THE CHARACTER RATE IS 9600 HZ. EACH BIT IS
  72. DIVIDED INTO 8 SMALL BITS SO THE NUMBER OF BITS PER SECOND REQUIRED
  73. FOR OUR SYSTEM IS 9600*8 = 76800 OR 7600 HZ.
  74. T = 1/7680 = 13 MICROSECOND
  75. THE CLOCK FREQUENCY IS 8000000 HZ.
  76. WE NEED TO DIVIDE THE CLOCK FREQUENCY BY 104 TO GENERATE A FREQUENCY
  77. OF 76800 HZ.
  78. 8000000/76800 = 104 = 13*8
  79. "DTCNT" COUNTS 8, AND "BAUD" COUNTS 13. TO GET 104 COUNTS WE NEED TO
  80. COUNT FROM 0 TO 103. BECAUSE THERE IS ONE CLOCK CYCLE DELAY UNTIL THE
  81. DATA IS AVAILABLE ON THE OUTPUT PINS (REGISTERED PAL), MODULE 104 IS
  82. DETECTED BY COUNT 102 WHICH IS EQUAL TO 102/8 = 12 6/8.