MTX-DIN Family
www.mtxm2m.com
2015/10 v2.3
Page
49
/
103
MTX M2M® by MATRIX ELECTRONICA S.L.U
4.2.6
SPI bus
The SPI bus (Serial Peripheral Interface) is a synchronous serial interface for control and data transfer
between the MTX-DIN modem and the connected application. Only one application can be
connected to the module’s SPI. The interface supports transmission rates of up to 6.5Mbps. It
consists of four lines: the two data lines SPIDI/SPIDO, the clock line SPICLK and the chip select line
SPICS.
The MTX-DIN modem acts as a single master device, e.g. the clock SPICLK is driven by the modem.
Whenever the SPICS pin is in a low state, the SPI bus is activated and data can be transferred from
the module and vice versa. The SPI interface uses two independent lines for data input (SPIDI) and
data output (SPIDO).
To configure and activate the SPI bus use the AT^SSPI command. If the SPI bus is active the two lines
I2CCLK and I2CDAT are locked for use as SPI lines.
SPI supports four operation modes. The modes are different in clock phase and clock polarity. The
module’s SPI mode can be configured by using the AT command AT^SSPI. Make sure the module and
the connected slave device works with the same SPI mode. The following picture shows the
characteristics of the four SPI modes. The SPI modes 0 and 3 are the most commonly used modes.
The SPI interface is only available if pins 1 and 6 of the I/O interface connector are not used as an I2C
interface.
