Octagon 6000 Series, User Manual

Page: 54 / 233

5-5
6000 Series user’s manual Serial ports
PC mode/network mode
On powerup, the BIOS extension reads the “N” position at W1 to deter-
mine which COM2 mode to select.
Table 5-2 COM2 mode select
“N” position at W1 Mode Description
Jumpered PC mode Use default configuration for
COM2 of 2400 baud, 8 data bits,
1 stop bit, and no parity.
Not jumpered Network mode Install IRQ3 vector.
Change default baud rate to
38.4 KB.
Read serial EEPROM bytes
120h,121h to determine if an ID
has been previously established.
If it has, use the existing ID, if
not, use FFh.
Discard messages addressed to
other nodes. Selectively respond
to messages addressed to node.
Await INT 17H BIOS calls to
collect messages.
COM2 as RS-232 I/O
COM2 is a standard RS-232 serial port, default configured at port
address 2F8H.
The “N” position at W1 distinguishes the COM2 mode on powerup. PC
mode (“N” position at W1 jumpered, default) configures COM2 as a
standard RS-232 port.
COM2 as RS-422/485
The PC Microcontrollers feature a predefined, easy-to-use software
interface for using COM2 as an RS-422/485 port. This software inter-
face supports Optomux type message-passing as well as additional
Octagon messages. Up to 32 nodes are supported at a default baud rate
of 38.4 KB. This built-in feature provides a simple, low cost, and effec-
tive method of rapidly implementing an RS-422/485 network. An Octa-
gon network interface module and an opto-isolated RS-232 to
RS-422/485 converter (Octagon P/N 4820), is required to convert RS-232
signals to RS-422/485.
Network mode (“N” position at W1 not jumpered) configures COM2 to
communicate at 38.4 KB, respond to Optomux type commands, respond
to Octagon commands and automatically perform network housekeeping
functions.