MCP4641 datasheet(55/92 Pages) MICROCHIP

55 / 92 page

DS22107A-page 55

MCP454X/456X/464X/466X

7.0

DEVICE COMMANDS

The MCP4XXX’s I2C command formats are specified in

this section. The I2C protocol does not specify how

commands are formatted.

The MCP4XXX supports four basic commands.

Depending on 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 Non-Volatile wiper EEPROM, general purpose

data EEPROM, and the TCON Register these com-

mands 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 Wiper-

Lock 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 Com-

mands, 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 com-

mands and their interaction with other device features.

7.1

Command Byte

The MCP4XXX’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 Table 7-1. C1:C0 determines if the

desired

memory

location

will

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 MCP4XXX will generate a Not

Acknowledge pulse to indicate the invalid combination.

The I2C Master device must then force a Start Condi-

tion to reset the MCP4XXX’s 2C 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 it’s MSb.

FIGURE 7-1:

Command Byte Format.

Command

# of Bit

Clocks (1)

Operates on

Volatile/

Non-Volatile

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

non-volatile memory write cycle has

completed.

High Voltage Increment and Decrement

commands on select non-volatile 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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