Artesyn RTM ATCA-F140 Installation and Use (July 2014) - Manual (Page 35)

Functional Description
RTM-ATCA-F140 Installation and Use (6806800M97F) 35
4.2.3 LEDs
The RTM-ATCA-F140 provides four panel-visible LEDs that provide the standard ATCA
management LED functions:
 Red - Out of Service
 Green - In Service
 Blue - Hot swap (initializing / shutting down)
 Amber - Attention
The LEDs are controlled by a PCF8574-type I2C parallel I/O expander. The ports of this are
connected as shown below.
The I/O expander interrupt line is not connected.
For the red, green and amber LEDs the cathodes are connected directly to the I/O expander
pins and the anodes are connected to the management 3.3V supply through current limiting
resistors selected to limit the LED current to 15mA. Since the I/Os power-up in the high state,
this ensures that the LEDs will remain off until explicitly turned on by the IPMC.
For the blue LED an external FET inverter is used to ensure the LED is on at power-up and a
charge pump is used to provide adequate forward voltage in the case the LED cannot be
operated directly from 3.3V.
Table 4-2 PCF 8574 Port Usage
Port Direction Connection
0 Output H/S LED (Blue)
1 Output OOS LED (Red)
2 Output IS LED (Green)
3 Output ATTN LED (Amber)
4 Output OOS LED (Amber)
5 Output FPGA PROM select
6 N/A (not connected)
7 Input FPGA DONE