Campbell CR23X, Operator'S Manual

Page: 84 / 374

SECTION 6. 9-PIN SERIAL INPUT/OUTPUT
6-6
6.2.6.1 SC32A INTERFACE TO COMPUTER
Most computers require the SC32A Optically
Isolated RS-232 Interface to communicate to the
CS I/O port. (Direct connection to the CR23X is
allowed through the “Computer RS-232” port.)
The SC32A can pass data up to 19.2 K baud.
The SC32A raises the CR23X's ring line when it
receives characters from a modem, and converts
the CR23X's logic levels (0 V logic low, 5V logic
high) to RS-232 logic levels.
The SC32A 25-pin port is configured as Data
Communications Equipment (DCE) (see Table
6.2-3) for direct connection to Data Terminal
Equipment (DTE), which includes most PCs
and printers.
When the SC32A receives a character from the
terminal/computer (pin 2), 5 V is applied to the
datalogger Ring line (pin 3) for one second or
until the Modem Enable line (ME) goes high.
The CR23X waits approximately 40 seconds to
receive carriage returns, which it uses to
establish baud rate. After the baud rate has
been set the CR23X transmits a carriage return,
line feed, "
∗
", and enters the Telecommunica-
tions Command State (Section 5). If the
carriage returns are not received within the 40
seconds, the CR23X "hangs up".
TABLE 6.2-3. SC32A Pin Description
PIN = Pin number
O = Signal Out of the SC32A to a peripheral
I = Signal Into the SC32A from peripheral
25-PIN FEMALE PORT:
PIN # I/O ABBREVIATION
1 GROUND
2 I TX
3 O RX
4 I RTS (POWER)
5 O CTS
6 O DSR
7 GROUND
8 O DCD
20 I DTR (POWER)
9-PIN MALE PORT:
PIN # ABBREVIATION
1 +5V INPUT
2 GROUND
3 RING
4 RX
5 ME
6 SDE
9 TX
NOTE: The SC32A has a jumper, which
when used, passes data only when the ME
line is high and the SDE line is low. The
function of the jumper is to block data sent
to SDs from being received by a
computer/terminal used to initiate data
transfer. Synchronous data will appear as
garbage characters on a computer/terminal.
6.2.6.2 SC932 INTERFACE TO MODEMS
Most modems have an RS-232 port configured as
DCE. For connection of the CS I/O port to DCE
devices such as modems and some computers,
the SC932 9-pin to RS-232 DCE Interface should
be used. The SC932 supports baud rates up to
19.2 K. Faster baud rates may be possible,
depending on the device being interfaced.
6.2.6.3 COMPUTER/TERMINAL
REQUIREMENTS
Computer/terminal peripherals are usually
configured as Data Terminal Equipment (DTE).
Pins 4 and 20 are used as handshake lines,
which are set high when the serial port is
enabled. Power for the SC32A RS-232 section
is taken from these pins. For equipment
configured as DTE (see Table 6.2-4) a direct
ribbon cable connects the computer/terminal to
the SC32A. Clear to Send (CTS) pin 5, Data
Set Ready (DSR) pin 6, and Data Carrier Detect
(DCD) pin 8 are held high by the SC32A (when
the RS-232 section is powered) which should
satisfy hardware handshake requirements of
the computer/terminal.
Table 6.2-4 lists the most common RS-232
configuration for Data Terminal Equipment.