MX844

9

08/25/06

Drawing No. 084423

www.claremicronix.com

IXYS

MX844

ADC_1 REGISTER, A[2:0] = 100 binary

7

DRDY status

0 = data ready

1 = data not ready

6

CMP status

0 = ADC data outside the comparator window

1 = ADC data inside the comparator window

5

reserved

4

reserved

3

ADC data D11

2

ADC data D10

1

ADC data D9

0

ADC data D8

ADC_2 REGISTER, A[2:0] = 101 binary

7:0

ADC data D[7:0]

Note: Reading this address sets the DRDY and CMP status bits to logic 1 and pins DRDY and CMP = high.

EXTERNAL SERIAL EEPROM PROGRAMMING

In this mode the MX844 auto-increments the EEPROM address from 0 up to 7 and then the address rolls

back to 0. A single EEPROM word is read at the beginning of every ADC auto-zero period and is

interpreted by the MX844 as a synchronous serial I/O write command. These commands control the

scanning sequence of the ADC channels, the full scale ranges, and the internal dividers. The MX844

accesses the EEPROM as if it were a ROM and will not write or erase the EEPROM. In the master mode

the first data bit serially read out of the EEPROM must always be a logic 1 which indicates a write (of the

MX844 register). The second through fourth bits are the address field, followed by eight data bits. The

last four bits of the EEPROM word are don't cares.

One 16-bit word of the 93C46 serial EEPROM is used to hold one MX844 synchronous serial I/O

instruction. Each pulse of SCK corresponds to one bit in the EEPROM. However, the data is aligned

such that the MX844 R/W bit that occurs at the 5th SCK pulse of the serial interface timing is the MSB in

the EEPROM word. The last 4 bits of the EEPROM word are always zero. For example, the instruction

to write the byte 1Ah into the MX844 control register (IN2 +/-250mV scale) would be programmed into the

EEPROM as the 16-bit quantity 81A0h. Entered into a typical programmer file editor in the least-

significant-byte first format it would be the byte A0h followed by the byte 81h. Eight pairs of bytes can be

specified in the programming file (EEPROM address 0 to 7). The MX844 will ignore the remaining

contents of the EEPROM (address > 7).

MX844 command:

R/W A2 A1 A0 B7 B6 B5 B4 B3 B2 B1 B0

1

0

0

0

0

0

0

1

1

0

1

0

8

1

A

EEPROM programmer editor:

B3 B2 B1 B0

0 0 0 0

R/W A2 A1 A0

B7 B6 B5 B4

A

0

8

1