B&B Electronics Parallel Port Input/Output Converter PPIO User Manual
Page 7
PPIO2899 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
5
Table 1
Note 1: X means no connection to any DB-25 pin.
Note 2: Bit 4 of 37AH as an output is used to control the interrupt IRQ7.
When this bit is HIGH, IRQ7 is enabled and when this bit is LOW, IRQ7 is
disabled. As an input, this reads the status of the IRQ7 interrupt to see if it
is enabled or not.
Note 3: The “bars” over the top of some pin numbers indicate that those
signals are inverted (in hardware) from PC's bus to DB-25 pin.
You can also read pins 1, 14, 16, and 17 using the INP(&H37A)
command. For this to work properly, you must first force all the
outputs HIGH. The way the parallel port is wired, if you do not force
the outputs HIGH they will interfere with the inputs. To do this, use
the command OUT &H37A,&H04 (04H is the same as 00000100
binary). Pins 1, 14, and 17 are inverting so a ZERO written to them
forces them HIGH. Pin 16 is non-inverting so the ONE written to it
forces it HIGH. After issuing the OUT command you can then do a
A2=INP(&H37A) that will read the TTL levels on those pins. In this
case the four upper bits (bits 4-7) will be unknown, but will probably
be HIGH.
378H
379H
37AH
BIT
Output
Input
Output
Input
Output
Input
0
2
2
X
X
_
1
_
1
1
3
3
X
X
_
14
_
14
2
4
4
X
X
16
16
3
5
5
X
15
_
17
_
17
4
6
6
X
13
See
Note 2
See
Note 2
5
7
7
X
12
X
X
6
8
8
X
10
X
X
7
9
9
X
_
11
X
X