HDSP-2301 HP [Agilent(Hewlett-Packard)], HDSP-2301 Datasheet - Page 21

• Manufacturer Part Number: HDSP-2301
• Description: Four Character 5.0 mm (0.20 inch) 5 x 7 Alphanumeric Displays
• Manufacturer: HP [Agilent(Hewlett-Packard)]

Figure 7. 8080A Microprocessor Program Utilizing a 160 Byte RAM Buffer that Interfaces to the REFRESH
CONTROLLER (cont.)
STORE MACHINE STATUS ON STACK
CDVR
TURN OFF COLUMN DRIVERS
RDVR
STORE BYTE OF DECODED DATA IN 74165
POINT
UPDATE POINT WITH ADDRESS OF
NEXT BYTE
CDVR
TURN ON APPROPRIATE COLUMN DRIVER
COLUMN
UPDATE COLMN FOR NEXT REFRESH CYCLE
FF
(POINT)
COLMN
POINT + 1
H
2 COLMN + 1
REFRESHED
YES
COLUMN 5?
NO
B
RFRSH
B
B = 0?
JUST
B –1
32
(END)
POINT
UPDATE POINT WITH ADDRESS
OF COLUMN 1 IN DECODED
DATA RAM
COLMN
UPDATE COLMN TO TURN
ON COLUMN 1
COUNT
OPTIONAL 2 ms TIMER
RESTORE MACHINE
STATUS FROM STACK
(FIRST)
(LOOP)
YES
NO
BUFFER
COUNT –1
FE
RETURN
H
ASCII
UPDATE ASCII WITH ADDRESS OF NEXT SYMBOL TO RIGHT
HL
LOAD HL WITH ADDRESS OF DECODER ROM
A
READ BYTE OF DECODED DATA FROM DECODER
(DE)
STORE BYTE OF DECODED DATA IN DECODED DATA RAM
HL
UPDATE HL WITH ADDRESS OF NEXT COLUMN IN DECODER
DE
UPDATE DE WITH ADDRESS OF NEXT COLUMN IN DECODED
DATA RAM
DE
UPDATE DE WITH ADDRESS FOR COLUMN 1 OF CHARACTER IN
DECODED DATA ROM IMMEDIATELY TO LEFT OF
PRECEEDING CHAR.
DE
LOAD DE WITH ADDRESS FOR COLUMN 1 RIGHTMOST
CHARACTER IN DECODED DATA RAM
(HL + A)
DECDR
HL + 80
DE + 32
DE – 161
A
ASCII + 1
BUFFER + 31
H
A
READ ASCII SYMBOL INTO A
(ASCII)
YES
YES
B
C
RETURN
13
C
B = 0?
C = 0?
LOAD
B
B –1
C –1
32
5
(LOOP 2)
(LOOP 1)
NO
NO