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Technical Description
Omega Engineering OMG-COMM8-A Page 9
Technical Description
The Sealevel OMG-COMM8-A provides 8 additional serial ports for
terminals, modems, printers, etc. The OMG-COMM8-A utilizes the
16550 UART chip. This chip features programmable baud rate, data
format, interrupt control and a 16 byte FIFO.
Features
• Eight RS-232 Ports with full modem control signals
• “PAL” addressing option allowing “Turn Key” configurations
• Selectable/Sharable Interrupts (IRQ’s 2/9-7,10,11,12,& 15 )
• Interrupt status port for Windows™ NT (listed in the NT Hardware
compatibility list) and Green Leaf™ COM: libraries
• 8 DB-25 male connectors provided using the Omega Engineering
“Octopus Cable”
Interrupt Status Port
The OMG-COMM8-A provides the user with an Interrupt Status Port
(ISP) for greater throughput when servicing multiple ports on a single
interrupt line. The ISP is a read only 8-bit register that sets a corresponding
bit when an interrupt is pending. Port 1 interrupt line corresponds with Bit
D0 of the status port, Port 2 with D1 etc.
The ISP can be addressed two different ways. If header E11 is in the
“Switch” position the Status Register is located at Base+7 on each port
(Example: Base = 280 Hex, Status Port = 287, 28F… etc.). This allows any
one of eight locations to be read to obtain the value in the status register.
All eight status ports on the OMG-COMM8-A are identical, so any one of
the eight can be read. If header E11 is in the “PAL” position, the status
port can be addressed at any location. Please contact Omega Engineering
for information on PAL programming and custom configurations.
Example: This indicates that Channel 2 has an interrupt pending.
Bit Position: 7 6 5 4 3 2 1 0
Value Read: 0 0 0 0 0 0
1
0