Intel Extensible Firmware Interface - Manual (Page 189)

Services — Boot Services
Version 1.10 12/01/02 5-91
GetNextMonotonicCount()
Summary
Returns a monotonically increasing count for the platform.
Prototype
EFI_STATUS
GetNextMonotonicCount (
OUT UINT64 *Count
);
Parameters
Count Pointer to returned value.
Description
The GetNextMonotonicCount() function returns a 64-bit value that is numerically larger
then the last time the function was called.
The platform’s monotonic counter is comprised of two parts:the high 32 bits and the low 32 bits.
The low 32-bit value is volatile and is reset to zero on every system reset. It is increased by 1 on
every call to
GetNextMonotonicCount() . The high 32-bit value is nonvolatile and is
increased by one on whenever the system resets or the low 32-bit counter overflows.
Status Codes Returned
EFI_SUCCESS The next monotonic count was returned.
EFI_DEVICE_ERROR The device is not functioning properly.
EFI_INVALID_PARAMETER One of the parameters has an invalid value.