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© Sealevel Systems, Inc. 3420 Manual | SL9145 9/2022
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
I
nterrupt
S
tatus
P
ort
(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
