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AC75 Hardware Interface Description
Strictly confidential / Preliminary
3.14
SPI Interface
The SPI (serial peripheral interface) is a synchronous serial interface for control and data
transfer between the AC75 module and the connected application. Only one application can
be connected to the module's SPI. The interface supports transmission rates up to 6.5Mbit/s.
It consists of four lines, the two data lines SPIDI/SPIDO, the clock line SPICLK and the chip
select line SPICS.
The AC75 module acts as a single master device, e.g. the clock SPICLK is driven by module.
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).
GSM module
SPIDI
SPIDO
SPICS
SPICLK
To configure and activate the SPI bus use the AT^SSPI command. If the SPI bus is active
the two lines I2CCLK and I2DAT are locked for use as I
AT^SSPI command as well explanations on the SPI modes required for data transmission
can be found in [1].
In general, 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.
Figure 22 shows the characteristics of the four SPI modes. The SPI modes 0 and 3 are the
most common used modes.
For electrical characteristics please refer to Table 26.
AC75_HD_V00.202
Figure 21: SPI interface
2
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s
Application
SPIDI
SPIDO
SPICS
SPICLK
C lines. Detailed information on the
27.04.2006
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