ICS Advent COMM4AT/EX, Product Manual

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Manual Number: 00750-123-1 Page 6
COMM4AT/EX Manual
Interrupt Modes
Headers J1A through J4A select the interrupt modes for each port. Each port must be set in the
correct mode to insure proper operation.
‘ N ’ indicates the ( N )ormal, single interrupt per port mode. ‘ S ’ Indicates the ( S )hared interrupt
mode, which allows more than one port to access a single IRQ. ‘ M ’ indicates the inclusion of a 1K
ohm pull-down resistor required on one port when sharing interrupts.
1 6 0
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Figure 2: Header J1A, Normal IRQ Mode
Set the jumpers to ‘ S ’ for shared interrupt mode on all blocks sharing an IRQ except one. Set that
port block for ‘ M ’. This provides the pull-down resistor circuit that makes sharing IRQs possible.
If you are using more than one COMM4AT/EX or a compatible adapter in a bus you should only
have one port set to ‘ M ’. The following example shows two ports sharing a single IRQ.
1 6 0
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Figure 3: Header J1A & J2A, Shared IRQ Mode
Set the jumper to ‘ S ’ if you are using more than one COMM4AT/EX in a bus or to completely
remove the pull-down resistor for hardware compatibility. Setting the adapter in this configura-
tion when it is not accompanied by a pull-down resistor will prevent the ports from trigger-
ing an interrupt .
Clock Modes
The COMM4AT/EX employs a unique clocking option that allows the end user to select from
divide by 4, divide by 2 and divide by 1 clocking modes. This mode is selected at J5.
To select the Baud rates commonly associated with COM: ports (i.e. 2400, 4800, 9600, 19.2,
115.2K Bps) place the jumper in the divide by 4 mode (silk-screen DIV4).
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Figure 4: Clocking Mode ‘Divide By 4’