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85 lines
4.0 KiB

PAL20X10 PAL DESIGN SPECIFICATION
VP6 BIRKNER/UDI 21/7/81
UART SHIFT REGISTER AND CONTROL KEY DETECT
MMI SUNNYVALE, CALIFORNIA
CK /SAMPLE RXD /CLRLIN /WRITE INIT NC NC NC NC NC GND
/UEN /BS /SPACE D6 D5 D4 D3 D2 D1 D0 /LF VCC
/D0 := /D0*/SAMPLE ;HOLD
+ SPACE ;SET SPACE CODE
:+:/D1* SAMPLE ;SHIFT
/D1 := /D1*/SAMPLE ;HOLD
+ SPACE ;SET SPACE CODE
:+:/D2* SAMPLE ;SHIFT
/D2 := /D2*/SAMPLE ;HOLD
+ SPACE ;SET SPACE CODE
:+:/D3* SAMPLE ;SHIFT
/D3 := /D3*/SAMPLE ;HOLD
+ SPACE ;SET SPACE CODE
:+:/D4* SAMPLE ;SHIFT
/D4 := /D4*/SAMPLE ;HOLD
+ SPACE ;SET SPACE CODE
:+:/D5* SAMPLE ;SHIFT
/D5 := /INIT*/D5*/SAMPLE*/SPACE ;SET SPACE CODE INSTEAD
+ /D5*/SAMPLE*/SPACE ;OF ANY CONTROL CODE
:+:/INIT*/D6*SAMPLE*/SPACE ;SHIFT
/D6 := /INIT*/D6*/SAMPLE ;HOLD
+ SPACE ;SET SPACE CODE
:+:/INIT* RXD*SAMPLE ;DATA IS SHIFTED IN
SPACE := WRITE*/D6*/D5 ;DETECT CTRL CHAR
+ CLRLIN ;AND CLEAR LINE
LF := /D6*/D5*/D4*D3*/D2*D1*/D0 ;LINE FEED = HEX 0A
*WRITE ;LATCH ON WRITE
+ LF*WRITE ;HOLD DURING WRITE
FUNCTION TABLE
CK SAMPLE RXD CLRLIN WRITE INIT /UEN /BS SPACE D6 D5 D4 D3 D2 D1 D0 LF
; S C
; A L W S
; M R R I / P
; P R L I N U / A
; C L X I T I E B C DATA OUT L
; K E D N E T N S E D6-----D0 F COMMENTS
-------------------------------------------------------------------------------
C X X L L L L X L XXXXXXX X INITIALIZE "SPACE"
C H X L L H L X L HHXXXXX X INITIALIZE D6 AND D5
C X X L L L L X L XXXXXXX X HOLD "SPACE" LO
C H L L X L L X L HXXXXXX X SHIFT IN 1'ST BIT OF "U" CODE
C H H L X L L X L LHXXXXX X SHIFT IN 2'ND BIT OF "U" CODE
C H L L X L L X L HLHXXXX X SHIFT IN 3'RD BIT OF "U" CODE
C H H L X L L X L LHLHXXX X SHIFT IN 4'TH BIT OF "U" CODE
C H L L X L L X L HLHLHXX X SHIFT IN 5'TH BIT OF "U" CODE
C H H L X L L X L LHLHLHX X SHIFT IN 6'TH BIT OF "U" CODE
C H L L X L L X L HLHLHLH X OUTPUT "U" CODE, STORE IN RAM
C H H L X L L X L LHLHLHL X SHIFT IN 1'ST BIT OF "LF" CODE
C H L L X L L X L HLHLHLH X SHIFT IN 2'ND BIT OF "LF" CODE
C H H L X L L X L LHLHLHL X SHIFT IN 3'RD BIT OF "LF" CODE
C H L L X L L X L HLHLHLH X SHIFT IN 4'TH BIT OF "LF" CODE
C H H L X L L X L LHLHLHL X SHIFT IN 5'TH BIT OF "LF" CODE
C H H L X L L X L LLHLHLH X SHIFT IN 6'TH BIT OF "LF" CODE
C H H L L L L X L LLLHLHL X DETECT "LF" CODE
C L X L H L L X H LLLHLHL H HOLD DURING WRITE
C L X L L L L X L LHLLLLL X WRITE "SPACE" CODE INTO RAM
-------------------------------------------------------------------------------
DESCRIPTION
THE "UART" SHIFT REGISTER IS A SEVEN BIT REGISTER FOR THE SEVEN BIT ASCII
CODE. THE INFORMATION ENTERS THE SHIFT REGISTER IN D6, ONE BIT AT A TIME.
IT COMES THROUGH RXD PIN WHICH IS THE TRANSMIT OR THE RECEIVE LINE OF THE
RS232. THE OUTPUTS ARE TRANSFERED IN PARALLEL TO THE RAM. "UEN" ENABLES THE
THREE STATE FOR THESE OUTPUTS. WHEN BITS D6 AND D5 TOGETHER IN THE ASCII
CODE ARE ZEROES OR WHE THE "CLRLIN" BIT IS SET, A "SPACE" CODE IS SHIFTED
INTO THE "UART" REGISTER. THE SPACE CODE PRINTS A BLANK SPACE ON THE SCREEN.
"SPACE" IN ASCII CODE IS 0100000 = 20 HEX.