UG-1262
Rev. B | Page 296 of 312
ALARM 0 REGISTER
Address: 0x40001414, Reset: 0xFFFF, Name: ALM0
ALM0 contains the lower 16 bits of the prescaled nonfractional WUT alarm target time value, where the overall alarm is defined as
ALM1, ALM0, and ALM2.
Any write to ALM0 pends until corresponding writes to ALM1 and ALM2 are carried out by the CPU, so that the combined 47-bit alarm
redefinition can be executed as a single transaction. ALM0, ALM1, and ALM2 can be written in any order, but coordinated, triple writes
must be carried out by the CPU to have any effect on the WUT alarm. ALM0 can be written to regardless of whether the ALMEN or
CNTEN bits are active in the CR0 register.
Table 385. Bit Descriptions for ALM0
Bits Bit
Name Settings Description
Reset Access
[15:0] VALUE
Lower 16 Prescaled Nonfractional Bits of the WUT Alarm Target Time. The alarm
register has a different reset value to the WUT count to avoid spurious alarms.
0xFFFF R/W
ALARM 1 REGISTER
Address: 0x40001418, Reset: 0xFFFF, Name: ALM1
ALM1 contains the upper 16 bits of the prescaled nonfractional WUT alarm target time value, where the overall alarm is defined as
ALM1, ALM0, and ALM2.
Any write to ALM1 pends until corresponding writes to ALM0 and ALM2 are carried out by the CPU, so that the combined 47-bit alarm
redefinition can be executed as a single transaction. ALM0, ALM1, and ALM2 can be written in any order, but coordinated, triple writes
must be carried out by the CPU to have any effect on the WUT alarm. ALM1 can be written to regardless of whether the ALMEN or
CNTEN bits are active in the CR0 register.
Table 386. Bit Descriptions for ALM1
Bits Bit
Name Settings Description
Reset Access
[15:0] VALUE
Upper 16 Prescaled Nonfractional Bits of the WUT Alarm Target Time. The alarm
register has a different reset value to the WUT count to avoid spurious alarms.
0xFFFF R/W
GATEWAY REGISTER
Address: 0x40001420, Reset: 0x0000, Name: GWY
GWY is a gateway MMR address through which the CPU can order actions to be taken within the WUT. The CPU does this by writing
specific keys to GWY. GWY reads back as all zeros. The WUT supports the following independent, software keyed commands:
Cancel all posted and executing write transactions in the WUT with immediate effect.
Capture a sticky snapshot of the CNT1, CNT0, and CNT2 MMRs into SNAP1, SNAP0, and SNAP2.
Table 387. Bit Descriptions for GWY
Bits Bit
Name Settings Description
Reset Access
[15:0] SWKEY
Software Keyed Command Issued by the CPU. This register is the write target for activating
software keyed commands issued by the CPU to the WUT. Supported keys are FLUSH_RTC
and SNAPSHOT_RTC. FLUSH_RTC is a software key of Value 0xA2C5 delivered via a
register write to GWY. FLUSH_RTC causes the WUT to flush all posted write transactions
and to immediately stop any transaction that it is currently executing. The CPU only
uses this key when power loss to the core is imminent and the CPU wants to cleanly and
quickly terminate communication activity across the power domain boundary before
the always on half of the WUT activates its isolation barrier. SNAPSHOT_RTC is a key of
Value 0x7627 delivered via a register write to GWY. SNAPSHOT_RTC causes the WUT to
take a sticky snapshot of the value of CNT1, CNT0, and CNT2 and store it in SNAP1,
SNAP0, and SNAP2. Snapshots are sticky until a new one is requested.
0x0 W