MAX1455CSLASHD datasheet(13/25 Pages) MAXIM

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Serial Digital Output

DIO is configured as a digital output by writing a Read

IRS (RDIRS) command (5 hex) to the CRIL location. On

receipt of this command, the MAX1455 outputs a byte of

data, the contents of which are determined by the IRS

pointer (IRSP[3:0]) value at location IRSA[3:0] = 8hex.

The data is output as a single byte, framed by a start bit

and a stop bit. Table 11 lists the data returned for each

IRSP address value.

Once the RDIRS command has been sent, all connec-

tions to DIO must be three-stated to allow the MAX1455

to drive the DIO line. Following receipt of the RDIRS com-

mand, the MAX1455 drives DIO high after 1 byte time.

The MAX1455 holds DIO high for a single bit time and

then asserts a start bit (drives DIO low). The start bit is

then followed by the data byte and a stop bit. Immediately

following transmission of the stop bit, the MAX1455 three-

states DIO, releasing the line. The MAX1455 is then

ready to receive the next command sequence 1 byte time

after release of DIO.

Note that there are time intervals before and after the

MAX1455 sends the data byte when all devices on the

DIO line are three-stated. It is recommended that a weak

pullup resistor be applied to the DIO line during these time

intervals to prevent unwanted transitions (Figure 4). In

applications where DIO and analog output (OUT) are not

connected, a pullup resistor should be permanently con-

nected to DIO. If the MAX1455 DIO and analog outputs

are connected, then do not load this common line during

analog measurements. In this situation, perform the fol-

lowing sequence:

1) Connect a pullup resistor to the DIO/OUT line, prefer-

ably with a relay.

2) Send the RDIRS command.

3) Three-state the user connection (set to high imped-

ance).

4) Receive data from the MAX1455.

5) Activate the user connection (pull DIO/OUT line high).

6) Release the pullup resistor.

Table 7. Input Referred Offset (IRO[2:0])

IRO SIGN, IRO[2:0]

INPUT-REFERRED OFFSET

CORRECTION AS % OF VDD

INPUT-REFERRED OFFSET, CORRECTION

AT VDD = 5VDC IN mV

1,111

+1.25

+63

1,110

+1.08

+54

1,101

+0.90

+45

1,100

+0.72

+36

1,011

+0.54

+27

1,010

+0.36

+18

1,001

+0.18

1,000

0,000

0,001

-0.18

-9

0,010

-0.36

-18

0,011

-0.54

-27

0,100

-0.72

-36

0,101

-0.90

-45

0,110

-1.08

-54

0,111

-1.25

-63

MAX1455

Low-Cost Precision Sensor Signal Conditioner

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