Rockwell Automation T8xxx Trusted Communications Interface - Manual (Page 51)

Trusted
TM
Communication Interface T8151B
Issue 21 Apr 10 PD-T8151B 51
Pin Function
(DTE) MP SK1 connection
1 RTS
2 TXD E14
3 RXD E16
4 CTS
5 GND
6 unconnected
Figure 19 MP and CI Front Panel Diagnostic Ports
6.1.1. Maximum Cable Length
The RS232 standard states that the maximum capacitive load seen by the driver should be 2500pF.
The maximum length of cable can be worked out from the capacitance specification of the cable being
used. For example, EIA Category 5 cable is rated at 17pF/ft so the maximum cable length will be
2500/17 = 147ft (approx. 45m). The maximum data rate for RS232 is 20Kbits/s (i.e. 19K2). As a
general rule, cable length may double if the data rate halves.