NXP Semiconductors UM11227 - 2 LF Control 2 Register (LFCTL2)

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
93 / 205
Field Description
1:0
SENS[1:0]
SENS[1:0] – Sensitivity Selection
The two bits SENS[1:0] select the sensitivity thresholds for the LFR input. These thresholds apply to the
detection portion of a message. If the input level is below the SNODET_x level, no signal will be detected. If
the level is above SDET_x, the signal will be detected. Sensitivity settings are only used in the carrier detect
path and do not affect reception of the message body.
0 0 = Very Low sensitivity (S
DET_VL
; S
NODET_VL
); Result of power on or LFR reset. Existing state remains
after all other reset types.
0 1 = Low sensitivity (S
DET_L
; S
NODET_L
)
1 0 = High sensitivity (S
DET_H
; S
NODET_H
)
1 1 = Very High sensitivity (S
DET_VH
; S
NODET_VH
)
10.15.17.2 LF control 2 register (LFCTL2)
Table 74. LF control 2 register (LFCTL2) (address $0021)
Bit 7 6 5 4 3 2 1 0
R
W
LFSTM3 LFSTM2 LFSTM1 LFSTM0 LFONTM3 LFONTM2 LFONTM1 LFONTM0
Reset U U U U U U U U
POR ($60) 0 1 1 0 0 0 0 0
LFR Soft
Reset ($60)
0 1 1 0 0 0 0 0
Table 75. LFCTL2 register field descriptions
Field Description
7:4
LFSTM[3:0]
LFSTM[3:0] – LF Sampling Time Interval Selection
The four bits LFSTM[3:0] select the length of time between when the LFR input detector is turned on as set
by the LFONTM bits in LFCTL2 register. The initial sampling interval starts with the LFO clock following a
write to these bits.
0 1 1 0 = Result of power on or LFR reset. Existing state remains after all other reset types.
See Table 76 for all states.
3:0
LFONT
M[3:0]
LFONTM[3:0] – LF Sampling On Time Selection The four bits LFONTM[3:0] select the length of time that
the LFR input detector is turned on at the beginning of each sampling interval set by the LFSTM bits. This
ON time is the net sampling time with any initialization time (maximum of 2 ms) included in the OFF time
prior to the sample ON time. If a signal is successfully detected, the length of time the detector remains ON
depends on the operating mode.
In carrier detect mode (CARMOD = 1) the detector will be turned off early if the evaluation of the carrier
signal is completed before the end of the scheduled ON time.
In data receive mode (CARMOD = 0) the detector will remain ON until the end of the message, an error is
detected or timeout occurrence.
The LFONTM selected time must be less than the LFSTM selected time, otherwise the Continuously ON
mode is present.
0 0 0 0 = Result of power on or LFR reset. Existing state remains after all other reset types.
See Table 77 for all states.