SMSC LAN9312 - Manual (Page 211)

High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9312 211 Revision 1.4 (08-19-08)
DATASHEET
14.2.5.11 GPIO 9 1588 Clock High-DWORD Capture Register (1588_CLOCK_HI_CAPTURE_GPIO_9)
This read only register combined with the GPIO 9 1588 Clock Low-DWORD Capture Register
(1588_CLOCK_LO_CAPTURE_GPIO_9) form the 64-bit GPIO 9 timestamp capture.
Offset: 168h Size: 32 bits
BITS DESCRIPTION TYPE DEFAULT
31:0 Timestamp High (TS_HI)
This field contains the high 32-bits of the timestamp upon activation of GPIO
9. RO 00000000h