6-4 Automating Measurements
Controlling Peripherals
Using the Parallel Port
Table 6-1 Writeable Ports
Port
Number
Register Description
15 0 Outputs 8-bit data to the Cent_D0 thru D7 lines of the Centronics port.
Cent_D0 is the least significant bit, Cent_D7 is the most significant bit.
Checks Centronics status lines for:
Out of Paper
Printer Not on Line
BUSY
ACKNOWLEDGE
15 1 Sets/clears the user bit according to the least significant bit of A. A least
significant bit equal to 1 sets the user bit high. A least significant bit of 0
clears the user bit.
15 2 Sets/clears the limit pass/fail bit according to the least significant bit of
A. A least significant bit equal to 1 sets the pass/fail bit high. A least
significant bit of 0 clears the pass/fail bit.
15 3 Outputs 8-bit data to the Cent_D0 thru D7 lines of the Centronics port.
Cent_D0 is the least significant bit, Cent_D7 is the most significant bit.
Sets the Printer_select signal high (de-select). Does not check
Centronics status lines.
9 0 Outputs a byte to the serial port. The byte is output serially according to
the configuration for the serial port.
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