NXP Semiconductors UM11227 - Tab. 148. SMI Control Register (SMIC) (Address $0041). 147 Tab. 149. SMIC Register Field Descriptions; SMI Control Register (SMIC)

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
147 / 205
Field Description
4
SEN
SEN — Sensor Acquisition Enable
When the SMI is idle, the SEN bit initiates an acceleration or pressure reading. When the SEN bit is set to 1,
a new acquisition cycle is started. When read, the SEN bit indicates the state of a measurement. If the SEN
bit is 0, the measurement is complete or idle; if the SEN bit is 1, the measurement is presently underway.
0 = Disable sensor (g-cell or p-cell) and C2V; Result of Reset
1 = Enable C2V and start measurement cycle
3
LPDM
LPDM — Low Power Direct Mode
The purpose of LPDM bit is to release the MCU of control the data acquisition and enter STOP4 mode
during direct mode. This allows the system to acquire data in the direct mode while in STOP4.
0 = Full Power Direct Mode Enabled. (RUN mode only); Result of Reset
1 = Low Power Direct Mode Enabled. (STOP4 allowed)
10.19.2.2 SMI control register (SMIC)
Table 148. SMI control register (SMIC) (address $0041)
Bit 7 6 5 4 3 2 1 0
R SCAP SPAR_ERR
W
SMIEN
1
SSEL1 SSEL0
—
reserved reserved reserved
Reset ($00) 0 0 0 0 0 0 0 0
Table 149. SMIC register field descriptions
Field Description
7
SMIEN
SMIEN — SMI Enable
The SMIEN bit controls the start of a sensor measurement without any automatic delay or trigger of the ADC
capture. This bit cannot be set to 1 if the SEN or LPDM bits are set to 1. To enter Direct Mode, the SEN
and LPDM bits should both be set to 0 before the SMIEN bit is set to 1. To exit Direct Mode, poll until the
SCAP bit is = 0. Then set the SMIEN to 0. Entering LPDM Mode requires multiple steps. First, any auto-
mode measurement cycle must be allowed to complete. Therefore, the SEN bit must be = 0. If the SEN bit
is <> 0, poll until it = 0. Next, set the LPDM bit to 1. Then, set the SMIEN bit to 1. Finally, in a subsequent
write command, set the SCAP bit to 1. To exit LPDM mode, set the SMIEN bit to 0, and then set the LPDM
bit to 0 on two consecutive writes. The SCAP bit will be automatically = 0 when LPDM bit goes to 0.
0 = SMI not in Direct or LPDM modes (i.e. idle); Result of Reset
1 = SMI in either Direct or LPDM mode (i.e. measurement in progress).
6
SCAP
SCAP — Sensor Capture
In auto-mode, i.e. when SEN is = 1, writing the SCAP bit will have no effect. In direct-mode, ADC
conversions are triggered by writing 1 to the SCAP bit. The bit is self-clearing. In LPDM mode, The SCAP
bit is set to 1 on entry to LPDM mode. Once written, the bit remains = 1 while a state machine automatically
generates triggers for the ADC. The SCAP bit will self-clear after the LPDM exit procedure of setting to 0 the
SMIEN and LPDM bits on two successive writes.
0 = ADC capture disabled; Result of Reset
1 = ADC capture enabled