DA6505.005
11 June 2018
FUNCTIONAL DESCRIPTION
Power on reset
The MAS6505 has power on reset (POR) circuitry
which resets the device into standby mode after both
power supplies VDD and VDDIO have risen to
sufficient levels. The VDD is supply voltage for
analog and digital blocks and the VDDIO is supply
voltage for the digital I2C and SPI serial bus
interface. There are no limitations for the slope and
sequence of raising of the VDD and VDDIO supplies.
However it is recommended to reset the device
manually after every power up to make sure it is
reset properly. This is accomplished via serial bus by
writing any data byte to the Reset register
(EC/6CHEX). See table 1 for MAS6505 memory
addresses. The POR or writing to the Reset register
will reset all registers from ED/6DHEX to FF/7FHEX to
a zero (00HEX) value.
Digital interface selection
The MAS605 supports I2C and SPI digital interfaces.
The I2C interface is a 2-wire serial bus which is
selected by leaving the CSB pin unconnected
(floating) or by connecting it to VDDIO. The CSB pin
has internal 250 kΩ pull-up resistor to VDDIO. Note:
The 2-wire I2C bus of MAS6505 supports only basic
I2C bus communication protocol but not for example
10-bit addressing, arbitration and clock stretching
features of the I2C bus specification.
bus mode. To select 3-wire SPI bus mode it is
necessary to first set WIRE=1 by writing to the
Configuration register.
The SPI communication is selected by pulling the
CSB pin low. It has an additional SPI mode lock in
feature. By pulling CSB low and giving at least four
SCK clock pulses makes the digital interface to lock
into SPI communication mode. This is done in order
to avoid inadvertently decoding SPI traffic to another
slave device as I2C data. After entering SPI lock
mode the I2C communication is possible only after
applying power on reset.
The SPI interface supports 3-wire and 4- wire serial
bus communication. Selection between 3- and 4-
wire SPI bus modes is done by WIRE bit in the
Configuration register (EE/6EHEX). See table 3. After
power up the WIRE=0 which selects the 4-wire SPI
8 (44)
MAS [ MICRO ANALOG SYSTEMS ]
