Appendix B. Serial Port Pinouts
Standard Null-Modem Cable Pin Out
Female
DB9
Socket
Female
DB9
Socket
1 & 6 ————— 4
2 ————— 3
3 ————— 2
4 ————— 1 & 6
5 ————— 5
7 ————— 8
8 ————— 7
9
most null modems have
no connection
1
9
1
If the null-modem cable does not connect pin 9 to pin 9, configure the
modem to output RING (or other characters previous to the DTR being
asserted) on the modem TX line to wake the CR800 and activate the DTR line
or enable the modem.
B.2.2 Power States
The RS-232 port is powered under the following conditions: 1) when the setting
RS232Power is set or 2) when the SerialOpen() for COMRS232 is used in the
program. These conditions leave RS-232 on with no timeout. If SerialClose() is
used after SerialOpen(), the port is powered down and left in a sleep mode
waiting for characters to come in.
Under normal operation, the port is powered down waiting for input. Upon
receiving input there is a 40 second software timeout before shutting down. The
40 second timeout is generally circumvented when communicating with
datalogger support software
(p. 86) because it sends information as part of the
protocol that lets the CR800 know it can shut down the port.
When in sleep mode, hardware is configured to detect activity and wake up. Sleep
mode has the penalty of losing the first character of the incoming data stream.
PakBus takes this into consideration in the "ring packets" that are preceded with
extra sync bytes at the start of the packet. SerialOpen() leaves the interface
powered-up, so no incoming bytes are lost.
When the logger has data to send via RS-232, if the data are not a response to a
received packet, such as sending a beacon, then it will power up the interface,
send the data, and return to sleep mode with no 40 second timeout.
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