Specifications
A second jumper option, W46, has
been
provided
to
allow
the
use
of
the printer port inter-
rupt
(IRQ
7)
as
an
extra interrupt
on
the
PC
Expansion Bus
if
you do not require interrupt-
based operation
of
the board's parallel printer port. The print functions in the board's ROM-
BIOS
do
not
use
the interrupt. However, some
PC
applications (e.g. spoolers) might require
printer interrupts,
SO-it-is-recommetKled--that
you leave this interrupt connected wdess you
aJ
e
certain it
is will not
be
needed.
To
free
IRQ
7 for
use
on
the
PC
Expansion Bus, cut the trace
shorting W46 (on the non-component side of the board).
IRQ
7 will now
be
available
on
the
PC
Expansion Bus, at J9 pin B21.
The
third jumper option, W47, allows the
use
of
the printer port -INIT signal
as
a Handshake
Out signal for the
V40
serial port.
If
that option is employed,
the
printer port must either not
be
used
for anything else,
or
must
be
used
in
a
manner
that
does
not
result
in
erroneous
handshake signal usage. As indicated in the table, shorting pin 1
to
pin 2 is the normal con-
fIguration,
which results in
the
Handshake
Out
signal being generated
by
the V40's internal
serial controller handshake logic.
2.4.4 PC Compatible Serial Port -
J3
The
PC
compatible serial port appears
at
header connector J3. Three RS232C output signals
and
fIve RS232C input signals facilitate connecting a
broad
range
of
serial devices
to
the
Little
Board/PC.
This
port
can
be
used for connection
of
a printer, modem, terminal,
or
other
serial device.
The
main
interface consideration is
that
the device
be
RS232C compatible.
Printers
and
modems generally require handshaking in one
or
both directions. Consult the serial device's
installation manual for information regarding possible handshake and other interface
consid-
erations.
Table 2-13 gives the board's connector pinout and signal dermitions.
In
addition, the pins to
which each signal should be wired for compatibility with the
COM
port external serial con-
nectors
of
PC's (DB25) and
ATs
(DB9) are also indicated.
Table 2-13. PC Serial Port Connections (J3)
J3
SIGNAL
FUNCTION
IN/aJT
DB25
DB9
PIN
NAME
PIN
PIN
1
DCD
Data
Carrier Detect in 8 1
2
DSR
Data
Set
Ready
in
6
6
3
RXD
Receive Data in 3 2
4
RTS
Request
To
Send
out 4
7
5
TXD
Data
OUtput
out
2
3
6
CTS
Clear
to
Send
in 5
8
7
DTR
Data
Terminal
Ready
out
2D
4
8
RI
Ring
Indicator in
22
9
9
GND
Signal
Gr<l'.Wld
. -
7 5
10
---
(no connection)
--
-- --
2-14