Impulse 3420 - Manual (Page 12)

Technical Description
Sealevel Systems COMM+8 Page 9
Technical Description
The Sealevel COMM+8 provides 8 additional serial ports for terminals,
modems, printers, etc. The COMM+8 utilizes the 16554 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 (IRQs 2/9-7,10,11,12, & 15 )
• 8 DB-9 or DB-25 male connectors provided using the Sealevel
Systems “Octopus Cable”
Interrupt Status Port
The COMM+8 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 COMM+8 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 Sealevel Systems 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