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© Sealevel Systems, Inc. 3541 Manual | SL9150 12/2022
Set the switch to ‘
S
’ for shared interrupt mode on all adapters sharing an IRQ. On one of the adapters sharing
an interrupt set the switches for both ‘
S
’ and for ‘
M
’. This provides the pull-down resistor circuit that makes
sharing IRQs possible. If you are using more than one compatible adapter in a bus, you should only have
one port set to ‘
M
’.
Header E1 (IRQ Selection)
The
C4-104.ULTRA
has a single interrupt selection jumper for all four of the ports, which should be set
prior to use, if an interrupt is required by your application software. Consult the user manual for the
application software being used to determine the proper setting.
Figure 2 - Header E1, IRQ Selection (IRQ 3 shown selected)
Clock Modes
The
C4-104.ULTRA
utilizes a 14.7456 MHz oscillator. This is eight times faster than the standard COM:
port oscillator, which typically is 1.8432 MHz. This allows the adapter to achieve a maximum data rate of
921.6Kbps. The following sections outline the baud rate calculations and instructions for achieving your
desired baud rate.
Baud Rates and Oscillator value
The following table shows some common data rates and the rates you should choose to achieve them
when using the
C4-104.ULTRA
. If the O/S of choice is Windows 95/98/ME/2000/NT/XP, the oscillator
value (14.7456 MHz) should be entered into the ‘Advanced Tab’ on 95/98/Me/2000/XP Device Manager
applet. Typically this is done automatically when the Sealevel Software driver is loaded.
When using Windows NT, the ‘Advanced Ports’ applet in the Control Panel should be launched and the
oscillator value entered manually in the ‘Advanced’ tab, or all data rates will be eight (8) times the selected
rate. For example if a data rate of 19.2Kbps is selected, the actual data rate will be 153.6Kbps.
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