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  1. PAL20X10 PAL DESIGN SPECIFICATION
  2. VP6 BIRKNER/UDI 21/7/81
  3. UART SHIFT REGISTER AND CONTROL KEY DETECT
  4. MMI SUNNYVALE, CALIFORNIA
  5. CK /SAMPLE RXD /CLRLIN /WRITE INIT NC NC NC NC NC GND
  6. /UEN /BS /SPACE D6 D5 D4 D3 D2 D1 D0 /LF VCC
  7. /D0 := /D0*/SAMPLE ;HOLD
  8. + SPACE ;SET SPACE CODE
  9. :+:/D1* SAMPLE ;SHIFT
  10. /D1 := /D1*/SAMPLE ;HOLD
  11. + SPACE ;SET SPACE CODE
  12. :+:/D2* SAMPLE ;SHIFT
  13. /D2 := /D2*/SAMPLE ;HOLD
  14. + SPACE ;SET SPACE CODE
  15. :+:/D3* SAMPLE ;SHIFT
  16. /D3 := /D3*/SAMPLE ;HOLD
  17. + SPACE ;SET SPACE CODE
  18. :+:/D4* SAMPLE ;SHIFT
  19. /D4 := /D4*/SAMPLE ;HOLD
  20. + SPACE ;SET SPACE CODE
  21. :+:/D5* SAMPLE ;SHIFT
  22. /D5 := /INIT*/D5*/SAMPLE*/SPACE ;SET SPACE CODE INSTEAD
  23. + /D5*/SAMPLE*/SPACE ;OF ANY CONTROL CODE
  24. :+:/INIT*/D6*SAMPLE*/SPACE ;SHIFT
  25. /D6 := /INIT*/D6*/SAMPLE ;HOLD
  26. + SPACE ;SET SPACE CODE
  27. :+:/INIT* RXD*SAMPLE ;DATA IS SHIFTED IN
  28. SPACE := WRITE*/D6*/D5 ;DETECT CTRL CHAR
  29. + CLRLIN ;AND CLEAR LINE
  30. LF := /D6*/D5*/D4*D3*/D2*D1*/D0 ;LINE FEED = HEX 0A
  31. *WRITE ;LATCH ON WRITE
  32. + LF*WRITE ;HOLD DURING WRITE
  33. FUNCTION TABLE
  34. CK SAMPLE RXD CLRLIN WRITE INIT /UEN /BS SPACE D6 D5 D4 D3 D2 D1 D0 LF
  35. ; S C
  36. ; A L W S
  37. ; M R R I / P
  38. ; P R L I N U / A
  39. ; C L X I T I E B C DATA OUT L
  40. ; K E D N E T N S E D6-----D0 F COMMENTS
  41. -------------------------------------------------------------------------------
  42. C X X L L L L X L XXXXXXX X INITIALIZE "SPACE"
  43. C H X L L H L X L HHXXXXX X INITIALIZE D6 AND D5
  44. C X X L L L L X L XXXXXXX X HOLD "SPACE" LO
  45. C H L L X L L X L HXXXXXX X SHIFT IN 1'ST BIT OF "U" CODE
  46. C H H L X L L X L LHXXXXX X SHIFT IN 2'ND BIT OF "U" CODE
  47. C H L L X L L X L HLHXXXX X SHIFT IN 3'RD BIT OF "U" CODE
  48. C H H L X L L X L LHLHXXX X SHIFT IN 4'TH BIT OF "U" CODE
  49. C H L L X L L X L HLHLHXX X SHIFT IN 5'TH BIT OF "U" CODE
  50. C H H L X L L X L LHLHLHX X SHIFT IN 6'TH BIT OF "U" CODE
  51. C H L L X L L X L HLHLHLH X OUTPUT "U" CODE, STORE IN RAM
  52. C H H L X L L X L LHLHLHL X SHIFT IN 1'ST BIT OF "LF" CODE
  53. C H L L X L L X L HLHLHLH X SHIFT IN 2'ND BIT OF "LF" CODE
  54. C H H L X L L X L LHLHLHL X SHIFT IN 3'RD BIT OF "LF" CODE
  55. C H L L X L L X L HLHLHLH X SHIFT IN 4'TH BIT OF "LF" CODE
  56. C H H L X L L X L LHLHLHL X SHIFT IN 5'TH BIT OF "LF" CODE
  57. C H H L X L L X L LLHLHLH X SHIFT IN 6'TH BIT OF "LF" CODE
  58. C H H L L L L X L LLLHLHL X DETECT "LF" CODE
  59. C L X L H L L X H LLLHLHL H HOLD DURING WRITE
  60. C L X L L L L X L LHLLLLL X WRITE "SPACE" CODE INTO RAM
  61. -------------------------------------------------------------------------------
  62. DESCRIPTION
  63. THE "UART" SHIFT REGISTER IS A SEVEN BIT REGISTER FOR THE SEVEN BIT ASCII
  64. CODE. THE INFORMATION ENTERS THE SHIFT REGISTER IN D6, ONE BIT AT A TIME.
  65. IT COMES THROUGH RXD PIN WHICH IS THE TRANSMIT OR THE RECEIVE LINE OF THE
  66. RS232. THE OUTPUTS ARE TRANSFERED IN PARALLEL TO THE RAM. "UEN" ENABLES THE
  67. THREE STATE FOR THESE OUTPUTS. WHEN BITS D6 AND D5 TOGETHER IN THE ASCII
  68. CODE ARE ZEROES OR WHE THE "CLRLIN" BIT IS SET, A "SPACE" CODE IS SHIFTED
  69. INTO THE "UART" REGISTER. THE SPACE CODE PRINTS A BLANK SPACE ON THE SCREEN.
  70. "SPACE" IN ASCII CODE IS 0100000 = 20 HEX.