DA6503.005
14 December 2016
2-WIRE SERIAL DATA INTERFACE (I2C BUS)
Conversion Result – Read Sequence
Table 11 presents a general control sequence for a
single register data (Dx) read from register address
(Ax).
Table 11. MAS6503 I2C bus single register (address Ax) read sequence bits
S
AW
A
Ax
A
Sr AR
A
Dx
N
P
Table 12 shows the control sequence for reading
the 24-bit A/D conversion result from the
Conversion result registers. The ISB (DI) and LSB
(DL) register data read can follow right after the
MSB register data (DM) read since if the read
sequence is continued (not ended by a Stop bit P)
since the register address is automatically
incremented to point to the next register.
Table 12. MAS6503 I2C bus MSB (first), ISB (second) and LSB (third) A/D conversion result read sequence
AW AM Sr AR DM DI DL
S
A
A
A
A
A
N
P
4-WIRE SERIAL DATA INTERFACE (SPI BUS)
SPI bus communication is selected by setting XSPI
pin low.
“Register and EEPROM data addresses”). In write
access bit A7 cleared (0) and in read access it is
set (1).
SPI communication differs from I2C bus in the
following way. It requires four wires for bi-directional
communication since each line operates in one
direction only. Device selection is done by using
separate chip select XCS control lines instead of
using device address. Each SPI bus device has its
own XCS control line and a device is selected by
pulling its XCS line low (see figure 5 below). The
fourth wire in the SPI bus is the serial clock line,
SCLK. Data is transferred at rising edges of the
serial clock during which the data line should be
stable.
Figure 5 illustrates write access communication.
MAS6503 has an auto increment function which
means that if there are more than one data byte
transferred the additional data bytes are delivered
to following register addresses. In write
communication the MISO line is high impedance.
In SPI bus communication it is good to note that
setting XCS low activates the EEPROM memory
regardless of the XSPI setting and the device
consumes 20A …30A current. To minimize
current consumption XCS should be set low only
during time periods when the device is used during
SPI communication.
The selection between write or read access is done
by register address MSB bit A7 (see table 1
XCS
SCLK
SCK
Register Address Byte
Data Byte
LSB
MSB
LSB
MSB
MOSI
SDA
High Z
MISO
Figure 5. SPI Protocol – Write Access (register address MSB bit A7=0)
23 (34)
MAS [ MICRO ANALOG SYSTEMS ]
