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; 0B0H = PORT3 DIRECT ADDRESSD_BUS DATA 0B0H ; data bus ( PORT 3 )

; 90H = PORT 1 DIRECT ADDRESSA_BUS DATA 90H ; address bus ( PORT 1 ),A0=P1.0,A1=P1.1,A2=P1.2

; 80H.0 = PORT 0 BIT 0 ( PORT0 BIT ADDRESS )WR BIT 80H.0; WR signal. to write to display A_BUS,data must bestable,

; then WR is brought LOW, data is written on LOW to HIGH; transition of WR. so we then bring WR to HIGH to

write.; PORT 0 BIT 1 DIRECT BIT ADDRESS

A3 BIT 80H.1; clear for brightness set, then set and leave set.; to set brightness send the following out to the data

D_BUS.; MSD-LSD 0=100% 1=80% 2=53% 3=40% 4=27% 5=20% 6=13%

7=blank

RST BIT 80h.2; Display Reset

;***************************************************************************;* FIRMWARE For Control Of The HDSP-2112 Display*;* A MOVING MESSAGE DISPLAY*;* FOR THE PHILLIPS 87C750 MICROCONTROLLER*;***************************************************************************

org 0 ; Establish Reset Vector at 0

; Routine to Reset Display on Power-Up

clr D_BUS.7; Enable Displayclr RST ; Reset & Clear Displaysetb wracall delay2 ; No Read or Write for at least 3 clock cycles

; after Reset & Clearsetb RST ; Hold RST High for remainder of program

; Set Display Brightness

bright: clr a3 ; clr A3 to setup for brightness setmov D_BUS,#7; data to blank displayclr wr ; WR=LOWsetb wr ; WR=HIGH, data written to display on LOW to

HIGHmov D_BUS,#6; 13% brightness

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clr wrsetb wrsetb a3 ; transition of WR pin, then we leave A3 set

for the; remainder of the program, as it is ONLY used

to; tell the display we want to set BRIGHTNESS.

count: mov r7,#4 ; Load R7 with the number of times+1 you wantyour

; message to be displayed before power down.; a 4 here will play the message 3 times etc...

count2: djnz r7,load ; Decrement counter, if not=zero goto loadajmp power_down ; else power down.

load: mov dptr,#message-1 ; load message address -1

begin: mov r0,#20h; beginning RAM address for storage +manipulation

mov r5,#8 ; #8=indicator of how many DIGITS the HDSP-2112 has

mov a,#20h ; ASCII equivalent of a BLANK space on display.

ramclr: mov @r0,a ; load ASCII BLANKS in display RAMinc r0 ; increment to next RAM addressdjnz r5,ramclr ; if we havent BLANKED out 8 address's keep

going

fetch: acall getchr ; RAM BLANK done , get first character to bediplayed

halt: jz count2 ; if return value in ACC = decimal 0 start overmov r5,#8 ; number of display DIGITS available on HDSP-

2112mov r0,#20h; load beginning RAM address

doit: xch a,@r0 ; SWAP ACC data with display RAM datainc r0 ; increment to next RAM addressdjnz r5,doit; check if END of RAM location, if not keep

goingmov r0,#20h; again load first RAM addressmov r4,#7 ; address to select first digit

; ( far right ) on displayacall msgout ; send message digit to displayajmp fetch ; return to routine FETCH.

msgout: clr d_bus.7; re-enable displaymov r5,#8 ; load number of digits our display has for

use.; notice here with R5 holding the starting

value; of 8, that this allows the routine MSGOUT1 to; decrement R4 8 times. R4 originally holds the; address for digit #8, or the ( RIGHT MOST ); digit on our display. By decrementing R4; we move the display digit ( ADDRESS ) from

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; digit to digit.; or from digit 8 to digit 1, from RIGHT TO

LEFT; as seen facing the display.

;NOTE: ( IF WE CHANGE R5 TO 7 THE DISPLAY WILLSCROLL

; TO DIGIT 2 THE SECOND FROM THE LEFT FACINGTHE

; DISPLAY ).

msgout1: mov a,r4 ; load digit address for display digitselection

mov A_BUS,a ; select digit position on displaydec r4 ; 1st digit=7 ( right side of display )

decrement formov a,@r0 ; next, then load ACC with data to display.mov D_BUS,a ; move data to displayclr wr ; WRITE STROBE for displaysetb wr ; write data to display on LOW to HIGH

transition

inc r0 ; increment RAM pointer to next data digit fordisplay

djnz r5,msgout1 ; if not=8 total digits keep goingacall delay2 ; delay to prevent JERKY look between digit

updates.; and to set our display ( SCROLL SPEED ).

ret ; return to calling routine.

getchr: inc dptr ; increment DPTR to point to next display digitclr a ; location ( MESSAGE ADDRESS ) in CODE space.movc a,@a+dptr; move CODE ( MESSAGE ) digit pointed to byret ; ACC+DPTR too ACC, and return to calling

routine.

power_down: mov 87h,#2 ; Set bit "PD" of the PCON Special FunctionRegister

; This will cause the controller to Power Down.

; routine DELAY2 sets the SCROLL SPEED, and will prevent a JERKYAPPEARANCE; between display digit updates. by changing the value first loaded into; R1 in the first line to a lower number the scroll speed is faster,and by; changing it to a higher number the scroll speed will be slower.

delay2: mov r1,#2

delay3: mov r2,#00hdelay4: mov r3,#00hdelay5: djnz r3,delay5

djnz r2,delay4djnz r1,delay3retnop

; the number 0 will indicate the END of our message.

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message: db ' Merry Christmas..............,'db ' And A Happy New Year..........',0

END