HDSP-2301 HP [Agilent(Hewlett-Packard)], HDSP-2301 Datasheet - Page 14

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

limits some of the software tech-
niques that can be used in the
main program.
The DECODED DATA CONTROL-
LER requires microprocessor
interaction only when the display
message is changed. Like the RE-
FRESH CONTROLLER, the ASCII
decoder is located within the mi-
croprocessor program. However,
the time required to decode the
ASCII string and store the result-
ing 5 x 7 display data into the
interface requires several millisec-
onds of microprocessor time.
Figure 3. Four Different Techniques to Interface the HDSP-2000 Alphanumeric Display to a Microprocessor System
** SCRATCHPAD WITH OR
** SCRATCHPAD
* PROGRAM + ASCII
* PROGRAM + ASCII
ADDRESS BUS
ADDRESS BUS
LOOKUP TABLE
WITHOUT DECODED ASCII
LOOKUP TABLE
LOOKUP TABLE
RAM**
RAM**
SYSTEM CLOCK
INTERRUPT
REQUEST
DATA
DATA
BUS
BUS
ROM*
ROM*
COUNTER
MUX
CLOCK
LATCH
500 Hz
PISO
REFRESH CONTROLLER
DECODER DATA CONTROLLER
CLOCK, 5 COLUMNS
DATA, CLOCK
5 COLUMNS
RAM
The CODED DATA CONTROL-
LER also requires interaction
from the microprocessor system
only when the display message is
changed. Because the ASCII de-
coder is located within the display
interface, the microprocessor re-
quires much less time to load a
new message into the display.
The DISPLAY PROCESSOR CON-
TROLLER, the HDSP-247X series,
is the most powerful interface.
The software within the DISPLAY
PROCESSOR CONTROLLER fur-
ther reduces the host
DISPLAY
DATA
DISPLAY
*** ASCII DECODER FOR CUSTOM FONT
** SCRATCHPAD
* PROGRAM
** SCRATCHPAD
* PROGRAM
ADDRESS BUS
RAM**
RAM**
SYSTEM CLOCK
ADDRESS BUS
DATA
DATA
BUS
BUS
ROM*
ROM*
microprocessor interaction by
providing more powerful left and
right data entry modes compared
to the RAM entry mode of the DE-
CODED DATA and CODED DATA
CONTROLLERS. The DISPLAY
PROCESSOR CONTROLLER can
also provide features such as a
Blinking Cursor, Editing Com-
mands, and a Data Out function.
One version of the DISPLAY PRO-
CESSOR CONTROLLER allows
the user to provide a custom
ASCII decoder for applications
needing a special character font.
6
DISPLAY PROCESSOR CONTROLLER
COUNTER
MUX
RAM CONTROLLER
DECODER
RAM
***
CLOCK, 5 COLUMNS
1/5
DECODER
DISPLAY
DISPLAY
5 COLUMNS
ASCII
PISO
CLOCK
DATA,
AN1016.03
DATA