PT AMC123, User Manual

Page: 54 / 104

Chapter 3: Getting Started
54
Programming the User LED
The AMC123 includes one bicolor (green/amber), user-defined LED located on the front panel,
labelled USR. See
Figure 2-1, “AMC123 Front Panel,” on page 23 for the LED identification.
The user LED is software programmable through GPIO bits 27 and 28 of the Intel EP80579
Integrated Processor GPO_BLINK enable register. The LED is turned off after a power cycle or
a reset.
As shown in Table 3-3, “User LED Control,” two bits each are used to control the state of the
LED. Since a bicolor LED is used, there are four states for the LED: green, amber, both colors
off and both colors on.
GPO Blink Enable Register
The GPIO can control the User LED with an optional blink at 1 second intervals.
The I/O address is 050Ch (0x0Ch) for LED control and 0518h (0x18h) for blink control. The I/O
Base register of device 0, function 31, Offset 0x48h needs to be checked to get the proper base
address for the user LED register control.
Note: The GPIO bits that control the user LED’s bits are in the same register as other system
critical functions. It is important not to change the state of other bits in this register when
modifying the user LED status.
Table 3-3: User LED Control
LED State
Bit Green Amber Both Off Both On
Bit 27 0 1 1 0
Bit 28 1 0 1 0