MAS6502 datasheet(12/20 Pages) MAS

12 / 20 page

DA6502.008

29 November 2012

12 (20)

SERIAL DATA INTERFACE (I

BUS) CONTROL

Conversion Starting – Write Sequence

Conversion is started by writing configuration bits

into the ADC control register. The write sequence is

illustrated in Table 8.

Table 8. MAS6502 I

® bus write sequence

Abbreviations:

AW = Device Write Address (%1110 1110)

AR = Device Read Address (%1110 1111)

AC = ADC Control Register Address (%1111 1111)

Ax = MSB (x=M, %1111 1101) or LSB (x=L, %1111

1110) ADC Result Register Address

DC = ADC Control Register Data

Dx = MSB (x=M) or LSB (x=L) ADC Result Register

Data

Each serial bus operation, like write, starts with the

start (S) bit (see figure 3). After start (S) the

MAS6502 device address with write bit (AW, see

table 7) is sent followed by an Acknowledge (A).

After this the ADC control register address (see

table 1) is sent and followed by an Acknowledge

(A). Next the ADC control register data (DC, see

table 2) is written and followed by an Acknowledge

(A). Finally the serial bus operation is ended with a

stop (P) command (see figure 3).

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 the A/D conversion period the input signal is

sampled

continuously

leading

output

conversion result that is a weighted average of the

samples taken. Note: The device should not be

addressed via serial bus before the conversion has

ended. Reading or writing to the device during the

conversion may corrupt the conversion result.

Conversion Result – Read Sequence

Table 9 shows a general control sequence for a

single register data read.

Table 9. MAS6502 I

® bus single register (address Ax) read sequence

Table 10 shows the control sequence for reading

the 16-bit A/D conversion result from both the MSB

and LSB data registers. The LSB register data (DL)

can be read right after the MSB register data (DM)

in case the read sequence is continued (not ended

by a Stop bit P) since the register address is

automatically incremented to point to the next

data register).

Table 10. MAS6502 I

® bus MSB (first) and LSB (second) A/D conversion result read sequence

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