Owners manual

System
H3 Datasheet(Revision1.2) Copyright© 2015 Allwinner Technology Co.,Ltd.All Rights Reserved. Page 166
Clock sources driving the watchdog timer must be controlled or managed by a trusted entity. This means that
non-trusted world accesses are not permitted to turn on, turn off or modify the characteristics of clock source. The
Clear Enable will reset relevant bits in the watchdog registers, except the reset flag.
4.7.3.2. NV-Counter
After a firmware image is validated, the image revision number taken from the certificate extension field, for example,
Trusted Firmware NV-Counter is compared with the corresponding NV-Counter stored in hardware. If the value is:
 Less than the associated NV-Counter, then the authentication fail.
 Identical to the NV-Counter, then the authentication is successful.
 More than the NV-Counter, then the authentication are successful and the NV-Counter is updated.
The 2^32 monotonic counter does not need to be e-Fuses, but it does need to be fully secure. Using the SoC
embedded NVM, or external secure element, or a trusted register, which is always on power.
The Secure Storage NV-Counter Register is used for protecting the trusted world Secure Storage (SST) file from replay
attacks, since SST contains subsidiary relay attacks protection counters for each Trusted Application.
Four 32-bit counters are used for counting 2^32 states for synchronizing data stores against replay attacks. These
counters are optionally required since they can be handled by a Trusted OS service using the secure storage at boot
time or using eMMC v4.4x Replay Protected Memory Block (RPMB).
4.7.4. TWD Register List
Module Name
Base Address
TWD
0x01F01800
Register Name
Offset
Description
TWD_STATUS_REG
0x0000
TWD Status Register
TWD_CTRL_REG
0x0010
TWD Control Register
TWD_RESTART_REG
0x0014
TWD Restart Register
TWD_LOW_CNT_REG
0x0020
TWD Low Counter Register
TWD_HIGH_CNT_REG
0x0024
TWD High Counter Register
TWD_INTV_VAL_REG
0x0030
TWD Interval Value Register
TWD_LOW_CNT_CMP_REG
0x0040
TWD Low Counter Compare Register
TWD_HIGH_CNT_CMP_REG
0x0044
TWD High Counter Compare Register
SST_NV_CNT_REG
0x0100
Secure Storage NV-Counter Register
SYN_DATA_CNT_REG0
0x0110
Synchronize Data Counter Register 0
SYN_DATA_CNT_REG1
0x0114
Synchronize Data Counter Register 1
SYN_DATA_CNT_REG2
0x0118
Synchronize Data Counter Register 2
SYN_DATA_CNT_REG3
0x011C
Synchronize Data Counter Register 3
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