DA6503.005
14 December 2016
2-WIRE SERIAL DATA INTERFACE (I2C BUS)
Figure 4. I2C bus protocol definitions
Bus communication includes Acknowledge (A) and
not Acknowledge (N) messages. To send an
acknowledge the receiver device pulls the SDA low
for one SCL clock cycle. For not acknowledge (N)
the receiver device leaves the SDA high for one
SCL clock cycle in which case the master can then
generate either a Stop (P) bit to abort the transfer,
or a repeated Start (Sr) bit to start a new transfer.
Abbreviations:
A= Acknowledge by Receiver
N = Not Acknowledge by Receiver
S = Start
P = Stop
= from Master (MCU) to Slave (MAS6503)
= from Slave (MAS6503) to Master (MCU)
Sr = Repeated Start
Conversion Starting – Write Sequence
Conversion is started by writing configuration bits
into the Measurement control registers 1 and 2
(addresses E2HEX and E3HEX). The write sequence
is illustrated in Table 10.
Table 10. MAS6503 I2C bus write sequence of two consecutive Measurement control registers 1 and 2
S
AW
A
MC1
A
DC1
A
DC2
A
P
Abbreviations:
AW = Device Write Address EAHEX (%1110 1010)
AR = Device Read Address EBHEX (%1110 1011)
MC1 = Meas. control reg.1 62HEX (%0110 0010)
Ax = Conversion Result Registers’ Addresses; MSB
(x=M, 67HEX %0110 0111), ISB (x=I, 68HEX %0110
1000) or LSB (x=L, 69HEX %0110 1001)
DC1 = Measurement Control Register 1 Data
DC2 = Measurement Control Register 2 Data
Dx = Conversion Result Register Data; MSB (x=M),
ISB (x=I) or LSB (x=L)
Each serial bus operation, like write, starts with the
start (S) bit (see figure 4). After start (S) the
MAS6503 device address with write bit (AW, see
table 9) is sent followed by an Acknowledge (A).
After this the Measurement control register 1
address (see table 1) is sent and followed by an
Acknowledge (A). Next the Measurement control
register 1 data (DC1, see table 3) is written and
followed by an Acknowledge (A). Due to register
address auto increment to the next register address
the Measurement control register 2 data (DC2, see
table 4) can follow right after first data byte. After
acknowledge of second data byte the serial bus
operation is ended with stop (P) command (see
figure 4). A new A/D conversion starts right after
Measurement control register 2 bits are received.
A/D Conversion
After power on reset or external reset (XCLR) the
EOC output is high. After an A/D conversion is
started the EOC output is set low until the
conversion is finished and the EOC goes back high,
indicating that the conversion is done and data is
ready for reading. The EOC is set low only by
starting a new conversion. To save power the
internal oscillator runs only during conversion.
During an A/D conversion the input signal is
sampled continuously leading to an output
conversion result that is a weighted average of the
samples taken.
22 (34)
MAS [ MICRO ANALOG SYSTEMS ]
