Agilent Technologies RS-232, Instruction Manual

Page: 15 / 28

RS-232 and RS-485 Options for the senTorr Gauge Controller
DRA
FT
1-1
RS-232 and RS-485 Options
The senTorr serial communication board is available in the following configurations:
❑
RS–232 standard with a 9-pin D-subminiature connector (Part number L6439-301)
❑
RS–485 (Part number L8940-301)
The last digit of the senTorr key entry determines the communication options installed
(Table 1-1).
Board Configurations
This section discusses board configuration and capabilities.
RS–232 standard version
All of the keypad functions, except for the baud rate settings and the display output, are
accessible through the RS–232 bidirectional computer link.
The standard RS–232 board contains a DIP switch that reverses the pin-outs of the RTS/CTS
and TXD/RXD pairs. This built-in, null modem capability is used to simplify the cable
connection to the host system.
The senTorr o9 V for an asserted (logic 0) level, and
−
9 V for an unasserted (logic 1)
level. The input signals to senTorr must be b2.4 V and +30 V for an asserted level
and +8 V and -30 V for an unasserted level.
Maximum cable length is 50’ (15.24 m).
RS–485
The RS–485 board employs differential line drivers and receivers capable of communicating
with up to 32 senTorr units, at distances of up to 4000’ (1219.2 m) at 19,200 baud in a
multidrop scheme. The network arrangement allows any unit to go offline without affecting
the operation of the other units. A shielded, twisted pair cable provides good resistance to
electrical noise. The cable multiplexes transmit and receive signals on one pair, leaving the
other pair available for RTS. The factory setting is for RS–485.
Table 1-1 Gauge Configuration Key Entries
Configuration Key Entry
No Communications 0
RS-232 1
RS-485 4