Repair manual

2-73
THEORY OF OPERATION
o Isolation (buffer) between the host computer and the Digital Palette
to prevent signals internal to the Digital Palette from feeding back to
the host computer. The interface network also cleans the data signals
from the host computer (inhibits any noise riding on the data signals
from being applied to the Digital Palette internal circuitry).
Refer to the provided Centronics Parallel Interface Specifications Manual
for a detailed description of the communication signals between the
Digital Palette and the host computer.
Table 2-14. Centronics Interface I/O Signal Lines
Pin # Name Function
1 STROBE This signal line transmits the STROBE pulse from the host
computer to the Digital Palette.
When the host computer asserts the STROBE pulse,the data
asserted on the DATA signal lines by the host computer is
transmitted to the Digital Palette for processing.
2 - 9 DATA Upon command from the host computer STROBE pulse, the data
asserted by the host computer is transmitted via the DATA signal
lines to the Digital Palette.
10 ACKNLG This signal line transmits the ACKNL signal from the Digital
Palette to the host computer to indicate that its transmitted data
was accepted.
Once the Digital Palette acknowledges receipt of the transmitted
data, the Digital Palette clears the BUSY signal line. The host
computer monitors this signal line to determine if its ok to resume
sending data.
11 BUSY This signal line transmits the asserted BUSY signal from the
Digital Palette to the host computer while data is being
transmitted. It prevents the host computer from sending more data
until the transmitted data has been accepted by the Digital Palette.
Once the host computer determines that the BUSY signal line is
cleared, data can again be asserted on the DATA signal lines and
strobed into the Digital Palette.