MC3630 Datasheet, PDF (27/83 Pages) –

MC3630 3-Axis Accelerometer
Preliminary Datasheet
5 Interfaces
SPI vs I2C Operation Modes
The device contains both I2C and SPI slave interfaces which share common pins. However,
only one interface can be active for correct device operation. Once the device completes POR
or a hard reset, both interfaces are active.
After power-up and any reset of the device (0x24[6] = 0x1), the first transaction to the
device must be to select I2C or SPI interface by writing to 0x1 into register 0x0D[6] for
I2C or 0x1 into register 0x0D[7] for SPI 4 wire or 0x1 into register 0x0D[5] for SPI 3 wire.
The situation where bits are set at the same time must be avoided or unstable device
operation could occur.
I2C Physical Interface
The I2C slave interface operates at a maximum speed of 1 MHz in I2C “Fast Mode Plus”. The
SDA (data) is an open-drain, bi-directional pin and the SCL (clock) is an input pin.
The device always operates as an I2C slave.
An I2C master initiates all communication and data transfers and generates the SCK_SCL
clock that synchronizes the data transfer. The I2C device address depends upon the state of
pin DOUT_A1 during power-up as shown in the table below.
7-bit Device ID 8-bit Address
(Write)
8-bit Address
(Read)
DOUT_A1 level
upon power-up
0x4C
(0b1001100)
0x98
0x99
GND
0x6C
(0b1101100)
0xD8
0xD9
VDD
Table 11. I2C Address Selection
The I2C interface remains active as long as power is applied to the VDDIO pin. In STANDBY
mode the device responds to I2C read and write cycles, but interrupts cannot be cleared. All
registers can be written in the SLEEP or STANDBY modes but in CWAKE mode, only the
(0x10) Mode Control Register can be modified.
Internally, the registers which are used to store samples are clocked by the sample clock and
gated by I2C activity. Therefore, in order to allow the device to collect and present samples in
the sample registers at least one I2C STOP condition must be present between samples.
Refer to the I2C specification for a detailed discussion of the protocol. Per I2C requirements,
when the I2C interface is enabled, DIN_SDA is an open drain, bi-directional pin. Pins
SCK_SCL and DIN_SDA each require an external pull-up resistor, typically 4.7kΩ.
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