Converting CST and WALLCLOCKTIME high/low to EPOCH

The only thing which I was given by the controls people at our company was this:
CurrentValue
LINT
GSV SSV
Current value of the wall clock time. DINT[0] contains the lower 32 bits of the value; DINT[1] contains the upper 32 bits of the value. The value is the number of microseconds that have elapsed since 0000 hours 1 January 1970. The CST and WALLCLOCKTIME objects are mathematically related in the controller. For example, if you add the CST CurrentValue and the WALLCLOCKTIME CTSOffset, the result is the WALLCLOCKTIME CurrentValue.

The key is the datatype: it's a 64-bit Long Integer.

ControlLogix controllers are fundamentally 32-bit devices, so they're just sending you the low and high 32-bit integers that make up that one 64-bit long integer. You'll have to reassemble them at a hex level, rather than interpreting them as 32-bit integers.

The information is the same as an Epoch value, except in microseconds instead of seconds. So divide by 1,000,000.

As an example, the Wallclocktime Current Value on my controller a moment ago is

CurrentValue[0] = 2095753508 = 0x7ceaa924 (hex)
CurrentValue[1] = 317577 = 0x0004d889 (hex)

Divide that number of microseconds 0x0004d8897ceaa924 (hex) by one million (0x000f4240) to get Seconds: 0x514cc21c (hex).

Run the hex value 0x514cc21c through a handy online Unix Epoch Converter, and I get Friday, March 22 at 1:45 PM Pacific Time.

Hi Ken, thank you for your help and explanation! This is working for me most of the time. When the PLC sends me a high value of 317516 and a low value of 469984752, I get the expected 3/19/2013 15:28:25 (I am adding the -4 hour EST timezone offset to the result). However, when I recieve a negative number for the low value, I am unsure of how to handle this, as I am unsure how it became a negative value.
For example, the PLC sent a high value of 317535 and low value of -1563843277 . The time should resolve to 3/20/2013 14:46:11 but it doesn't, of course this makes the number much different. I am not sure how to handle these negative low values.
A second issue I have run into is High 317516 Low 234362143 (converted to hex as 4D84C and DF8151F) gives me us of 317516234362143, which puts my date somewhere in the year 1972, when the date expected is
3/19/2013 15:24:30 . Not sure if I need to apply a padding charactor to the low hex value or what. I do apreciate any guidance that you can give me. Thank you.

You need to make sure your datatypes are unsigned, or use instructions that move the data as bytes, rather than attempting to interpret it as an integer.

I'm not at all familiar with Oracle so I can't say what that looks like.