Datasheet

SCA100T Series
VTI Technologies Oy Subject to changes 11/18
www.vti.fi Doc. nr. 8261800 Rev.A
• each bit is sampled on the rising edge of SCK (MOSI line)
• after the device is selected with the falling edge of CSB, an 8-bit command is received. The
command defines the operations to be performed
• the rising edge of CSB ends all data transfer and resets internal counter and command register
• if an invalid command is received, no data is shifted into the chip and the MISO remains in
high impedance state until the falling edge of CSB. This reinitializes the serial communication.
• data transfer to MOSI continues immediately after receiving the command in all cases where
data is to be written to SCA100T’s internal registers
• 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 and RDAY is 5300 samples per sec / channel
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 00000000 Measure mode (normal operation mode after power on)
RWTR 00001000 Read and write temperature data register
RDSR 00001010 Read status register
RLOAD 00001011 Reload NV data to memory output register
STX 00001110 Activate Self test for X-channel
STY 00001111 Activate Self test for Y-channel
RDAX 00010000 Read X-channel acceleration through SPI
RDAY 00010001 Read Y-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 affecting the operation. The 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 to the RWTR command in order to guarantee correct data. The data transfer is
presented in Figure 10 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.
7 6 5 4 3 2 1
0
7 6 5 4 3 2 1
0
CSB
SCK
MISO
MOSI
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
HIGH IMPEDANCE
COMMAND
DATA IN
DATA OUT
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