Configuration/Setup Bytes (Write Cycle)

A write cycle begins with the bus master issuing a

START condition followed by seven address bits (Figure

7) and a write bit (R/W = 0). If the address byte is suc-

cessfully received, the MAX1236–MAX1239 (slave)

issues an acknowledge. The master then writes to the

slave. The slave recognizes the received byte as the

set-up byte (Table 1) if the most significant bit (MSB) is

1. If the MSB is 0, the slave recognizes that byte as the

configuration byte (Table 3). The master can write either

one or two bytes to the slave in any order (setup byte,

then configuration byte; configuration byte, then setup

byte; setup byte or configuration byte only; Figure 9). If

the slave receives a byte successfully, it issues an

acknowledge. The master ends the write cycle by issu-

ing a STOP condition or a repeated START condition.

When operating in HS-mode, a STOP condition returns

the bus into F/S-mode (see the HS-Mode section).

2.7V to 3.6V and 4.5V to 5.5V, Low-Power,

4-/12-Channel, 2-Wire Serial, 12-Bit ADCs

______________________________________________________________________________________

13

B. TWO-BYTE WRITE CYCLE

SLAVE TO MASTER

MASTER TO SLAVE

S

1

SLAVE ADDRESS

A

71 1

W

SETUP OR

CONFIGURATION BYTE

SETUP OR

CONFIGURATION BYTE

8

P or Sr

1

A

1

MSB DETERMINES WHETHER

SETUP OR CONFIGURATION BYTE

S

1

SLAVE ADDRESS

A

71 1

W

SETUP OR

CONFIGURATION BYTE

8

P or Sr

1

A

1

MSB DETERMINES WHETHER

SETUP OR CONFIGURATION BYTE

A

1

8

A. ONE-BYTE WRITE CYCLE

NUMBER OF BITS

NUMBER OF BITS

Figure 9. Write Cycle

BIT 7

(MSB)

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

(LSB)

REG

SEL2

SEL1

SEL0

CLK

BIP/UNI

RST

X

BIT

NAME

DESCRIPTION

7

REG

Register bit. 1 = setup byte, 0 = configuration byte (see Table 2).

6

SEL2

5

SEL1

4

SEL0

Three bits select the reference voltage and the state of AIN_/REF (Table 6). Default to 000 at

power-up.

3

CLK

1 = external clock, 0 = internal clock. Default to 0 at power-up.

2

BIP/UNI

1 = bipolar, 0 = unipolar. Default to 0 at power-up (see the Unipolar/Bipolar section).

1

RST

1= no action, 0 = resets the configuration register to default. Setup register remains unchanged.

0

X

Don’t care, can be set to 1 or 0.

Table 1. Setup Byte Format