MCP4432 datasheet(61/100 Pages) MICROCHIP

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DS22265A-page 61

MCP444X/446X

7.0

DEVICE COMMANDS

The MCP44XX’s I2C command formats are specified in

this section. The I2C protocol does not specify how

commands are formatted.

The MCP44XX supports four basic commands. The

location accessed determines the commands that are

supported.

For the Volatile Wiper Registers, these commands are:

• Write Data

• Read Data

•Increment Data

•Decrement Data

For the Nonvolatile wiper EEPROM, general purpose

data EEPROM, and the TCON Register, these

commands are:

• Write Data

• Read Data

These commands have formats for both a single

command or continuous commands. These commands

are shown in Table 7-1.

Each command has two operational states. The

operational state determines if the device commands

control the special features (Write Protect and

WiperLock Technology). These operational states are

referred to as:

• Normal Serial Commands

• High-Voltage Serial Commands

TABLE 7-1:

I2C COMMANDS

Normal serial commands are those where the HVC pin

is driven to VIH or VIL. With High-Voltage Serial

Commands, the HVC pin is driven to VIHH. In each

mode, there are four possible commands.

Additionally, there are two commands used to enable

or disable the special features (Write Protect and Wiper

Lock Technology) of the device. The commands are

special cases of the Increment and Decrement

High-Voltage Serial Command.

Table 7-2 shows the supported commands for each

memory location.

Table 7-3 shows an overview of all the device

commands and their interaction with other device

features.

7.1

Command Byte

The MCP44XX’s Command Byte has three fields: the

Address, the Command Operation, and 2 Data bits

(see Figure 7-1). Currently only one of the data bits is

defined (D8).

The device memory is accessed when the Master

sends a proper Command Byte to select the desired

operation. The memory location getting accessed is

contained in the Command Byte’s AD3:AD0 bits. The

action desired is contained in the Command Byte’s

C1:C0 bits, see Figure 7-1. C1:C0 determines if the

desired memory location will be read, written,

Incremented (wiper setting +1) or Decremented (wiper

setting -1). The Increment and Decrement commands

are only valid on the volatile wiper registers, and in

High Voltage commands to enable/disable WiperLock

Technology and Software Write Protect.

If the Address bits and Command bits are not a valid

combination, then the MCP44XX will generate a Not

Acknowledge pulse to indicate the invalid combination.

The I2C Master device must then force a Start

Condition to reset the MCP44XX’s I2C module.

D9 and D8 are the most significant bits for the digital

potentiometer’s wiper setting. The 8-bit devices utilize

D8 as their MSb while the 7-bit devices utilize D7 (from

the data byte) as their MSb.

FIGURE 7-1:

Command Byte Format.

Command

# of Bit

Clocks (1)

Operates on

Volatile/

Nonvolatile

memory

Operation

Mode

Write Data

Single

Both

Continuous

18n + 11 Volatile Only

Read Data

Single

Both

Random

Both

Continuous

18n + 11 Both (2)

Increment

(3)

Single

Volatile Only

Continuous

9n + 11

Volatile Only

Decrement

(3)

Single

Volatile Only

Continuous

9n + 11

Volatile Only

Note 1:

“n” indicates the number of times the

command operation is to be repeated.

This command is useful to determine if a

nonvolatile memory write cycle has

completed.

High Voltage Increment and Decrement

commands on select nonvolatile memory

locations enable/disable WiperLock

Technology and the software Write

Protect feature.

MCP4XXX

COMMAND BYTE

= Write Data

= Increment

MSbits (Data)

= Decrement

= Read Data

Command Operation bits

Memory Address

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