MCP4531 datasheet(48/88 Pages) MICROCHIP

48 / 88 page

MCP453X/455X/463X/465X

DS22096A-page 48

6.2.4

ADDRESSING

The address byte is the first byte received following the

START condition from the master device. The address

contains four (or more) fixed bits and (up to) three user

defined hardware address bits (pins A2, A1, and A0).

These 7-bits address the desired I2C device. The

A7:A4 address bits are fixed to “0101” and the device

appends the value of following three address pins (A2,

A1, A0). Address pins that are not present on the

device are pulled up (a bit value of ‘1’).

Since there are up to three adress bits controlled by

hardware pins, there may be up to eight MCP4XXX

devices on the same I2C bus.

Figure 6-9 shows the slave address byte format, which

contains the seven address bits. There is also a read/

write bit. Table 6-2 shows the fixed address for device.

Hardware Address Pins

The hardware address bits

(A2, A1, and A0)

correspond to the logic level on the associated address

pins. This allows up to eight devices on the bus.

These pins have a weak pull-up enabled when the VDD

< VBOR. The weak pull-up utilizes the “smart” pull-up

technology and exhibits the same characteristics as the

High-voltage tolerant I/O structure.

The state of the A0 address pin is latch on POR/BOR.

This is required since High Voltage commands force

this pin (HVC/A0) to the VIHH level.

FIGURE 6-9:

Slave Address Bits in the

I2C Control Byte.

TABLE 6-2:

DEVICE SLAVE ADDRESSES

6.2.5

SLOPE CONTROL

The MCP45XX/46XX implements slope control on the

SDA output.

As the device transitions from HS mode to FS mode,

the slope control parmameter will change from the HS

specification to the FS specification.

For Fast (FS) and High-Speed (HS) modes, the device

has a spike suppression and a Schmidt trigger at SDA

and SCL inputs.

Device

Address

Comment

MCP45X1

‘0101 11’b + A0

Supports up to 2

devices. Note 1

MCP45X2

‘0101 1’b + A1:A0

Supports up to 4

devices. Note 1

MCP46X1

‘0101’b + A2:A1:A0 Supports up to 8

devices. Note 1

MCP46X2

‘0101 1’b + A1:A0

Supports up to 4

devices. Note 1

Note 1:

A0 is used for High-Voltage commands

and the value is latched at POR.

SA6A5 A4A3 A2 A1 A0 R/W

A/A

Start

bit

Slave Address

R/W bit

A bit (controlled by slave device)

R/W = 0 = write

R/W = 1 = read

A = 0 = Slave Device Acknowledges byte

A = 1 = Slave Device does not Acknowledge byte

“0” “1” “0” “1”

See Table 6-2

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