SCA61T Series
•
data transfer out from MISO starts with the falling edge of SCK immediately after the last bit of
the SPI command is sampled in on the rising edge of SCK
•
•
maximum SPI clock frequency is 500kHz
maximum data transfer speed for RDAX is 5300 samples per sec / channel
The SPI command can be either an individual command or a combination of command and data.
In the case of combined command and data, the input data follows uninterruptedly the SPI
command and the output data is shifted out parallel with the input data.
The SPI interface uses an 8-bit instruction (or command) register. The list of commands is given in
Table below.
Command
Name
Command
Format
Description:
MEAS
RWTR
RDSR
RLOAD
STX
00000000
00001000
00001010
00001011
00001110
00010000
Measure mode (normal operation mode after power on)
Read and write temperature data register
Read status register
Reload NV data to memory output register
Activate Self test for X-channel
RDAX
Read X-channel acceleration through SPI
Measure mode (MEAS) is standard operation mode after power-up. During normal operation, the
MEAS command is the exit command from Self test.
Read temperature data register (RWTR) reads temperature data register during normal
operation without effecting the operation. Temperature data register is updated every 150 µs. The
load operation is disabled whenever the CSB signal is low, hence CSB must stay high at least 150
µs prior the RWTR command in order to guarantee correct data. The data transfer is presented in
Figure below. The data is transferred MSB first. In normal operation, it does not matter what data is
written into temperature data register during the RWTR command and hence writing all zeros is
recommended.
CSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
SCK
DATA IN
COMM AND
MOSI
M ISO
0
0
7
6
6
5
5
4
3
2
2
1
1
DATA OUT
HIGH IM PEDANCE
7
4
3
Figure 10.
Command and 8 bit temperature data transmission over the SPI
Self test for X-channel (STX) activates the self test function for the X-channel (Channel 1). The
Internal charge pump is activated and a high voltage is applied to the X-channel acceleration
sensor element electrode. This causes the electrostatic force that deflects the beam of the sensing
element and simulates the acceleration to the positive direction. The self-test is de-activated by
giving the MEAS command.
Read X-channel acceleration (RDAX) accesses the AD converted X-channel acceleration signal
stored in acceleration data register X.
During normal operation, acceleration data registers are reloaded every 150 µs. The load
operation is disabled whenever the CSB signal is low, hence CSB must stay high at least 150 µs
prior the RDAX command in order to guarantee correct data. Data output is an 11-bit digital word
that is fed out MSB first and LSB last.
VTI Technologies Oy
www.vti.fi
Subject to changes
Doc. nr. 8261900
11/18
Rev.A
VTI [ VTI TECHNOLOGIES ]
