NXP Semiconductors
UM11227
NTM88 family of tire pressure monitor sensors
UM11227 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2020. All rights reserved.
User manual Rev. 6 — 24 April 2020
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f
Bus
(MHz)
PRDIV8
(Binary)
DIV5:0
(Decimal)
f
FLCK
(kHz)
Program/Erase Timing Pulse
(5 µs Min, 6.7 µs Max)
(µs)
200 kHz 0 0 200 5
150 kHz 0 0 150 6.7
10.24.9.2 FMC option registers (FOPT and NVOPT)
During reset, the contents of the nonvolatile location NVOPT are copied from FLASH into
FOPT. Bits 5 through 2 are not used and always read 0. This register may be read at any
time, but writes have no meaning or effect. To change the value in this register, erase
and reprogram the NVOPT location in FLASH memory as usual and then issue a new
MCU reset.
Table 187. FMC option registers (FOPT) (address $1821)
Bit 7 6 5 4 3 2 1 0
R KEYEN FNORED 0 0 0 0 SEC1 SEC0
W — — — — — — — —
Reset ($) 0 0 0 0
Table 188. FMC option registers (NVOPT) (address $FFBF)
Bit 7 6 5 4 3 2 1 0
R KEYEN FNORED 0 0 0 0 SEC1 SEC0
W — — — — — — — —
Reset 0 0 0 0 1 from
factory
1 erased
0 from
factory
1 erased
Table 189. FOPT and NVOPT register field descriptions
Field Description
7
KEYEN
KEYEN – Backdoor Key Mechanism Enable
When the read-only KEYEN bit is 0, the backdoor key mechanism cannot be used to disengage security.
The backdoor key mechanism is accessible only from user (secured) firmware. BDM commands cannot be
used to write key comparison values that would unlock the backdoor key.
0 = No backdoor key access allowed
1 = If user firmware writes an 8-byte value that matches the nonvolatile backdoor key (NVBACKKEY
through NVBACKKEY+7 in that order), security is temporarily disengaged until the next MCU reset.
6
FNORED
FNORED – Vector Redirection Disable
When the read-only FNORED bit is 1, then vector redirection is disabled.
0 = Vector redirection enabled
1 = Vector redirection disabled
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