Automating Measurements
Controlling Peripherals
Port
Number
15
Register
0
1
I
15
I
I
I
9
I
0
Table 7-4. Writeable Ports
Dsscription
Outputs
8-bit
data to the
CentJILl
thru
07
lines of the Centronics port. Cent-DO is the
least significant bit,
Cent-07
is the most significant bit. Checks Centronics status lines for:
Out of Paper
Printer Not on tine
BUSY
ACKNOWLEDGE
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.
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.
Outputs B-bit data to the Cent-DO thru 07 lines of the Centronics port.
Cent-DO
is the
least significant bit,
Cent-D7
is the most significant bit. Sets the Printer-select signal high
Ide-select].
Does not check Centronics status lines.
Outputs a byte to the serial port. The byte is output serially according to the configuration
for the serial port.
Table
7.5.
Readable Ports
Pert
Number
Rsuistsr
9
0
Reads the serial port.
Dsscription
15 0
Reads the
8-bit
data port Cent-DO thru 07.
15
1
Reads the user bit.
15 2
Reads the limit test pass/fail bit.
15
10 Reads the
8-bit
status port.
DO-Cent-acknowledge
Dl-Cent-busy
DZ-Cent-out-of-paper
DICent-on-line
D4-Cent-printer-err
7-55
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