Revision 6    HC900 Process & Safety Controller User and Installation Manual  175 
21 April 2017 
Table 26 – LED Indications on Controller CPUs  
Solid Red 
Blinking Yellow 
Blinking Red 
Solid Green 
Blinking Green 
Solid Yellow 
Failed 
Failed 
(Diagnostic Code; refer to Table 27.) 
PROGRAM Mode 
RUN Mode 
OFFLINE Mode/while Flash RAM 
programming 
For legacy systems, 
RS-232/RS-485 S1 port 
For new systems, RS-
485 S1 port 
XMT/RCV 
 
 
Yellow when transmitting, green when 
receiving. 
For legacy systems, 
RS-232/RS-485 S2 port 
For new systems, RS-
485 S2 port 
XMT/RCV 
 
Yellow when transmitting, green when 
receiving. 
Yellow (On/Off) 
Green (On/Off/Flash) 
On for 100Base-T, Off for 10Base-T 
On for connection, Off for no 
connection, Flash for activity 
Yellow (On/Off) 
Green (On/Off/Flash) 
On for 100Base-T, Off for 10Base-T 
On for connection, Off for no 
connection, Flash for activity 
Yellow (On/Off) 
Green (On/Off/Flash) 
On for 100Base-T, Off for 10Base-T 
On for connection, Off for no 
connection, Flash for activity