MCP413X datasheet(47/88 Pages) MICROCHIP

47 / 88 page

DS22060B-page 47

MCP413X/415X/423X/425X

7.0

DEVICE COMMANDS

The MCP4XXX’s SPI command format supports 16

memory address locations and four commands. Each

command has two modes. These are:

• Normal Serial Commands

• High-Voltage Serial Commands

Normal serial commands are those where the CS pin is

driven to VIL. High Voltage Serial Commands, CS pin is

driven to VIHH, for compatibility with systems that also

support the MCP414X/416X/424X/426X devices. High

Voltage Serial Commands operate identically to their

corresponding Normal Serial Command. In each

mode, there are four possible commands. These

commands are shown in Table 7-1.

The 8-bit commands (Increment Wiper and Decre-

ment Wiper commands) contain a Command Byte,

see Figure 7-1, while 16-bit commands (Read Data

and Write Data commands) contain a Command Byte

and a Data Byte. The Command Byte contains two data

bits, see Figure 7-1.

Table 7-2 shows the supported commands for each

memory location and the corresponding values on the

SDI and SDO pins.

Table 7-3 shows an overview of all the SPI commands

and their interaction with other device features.

7.1

Command Byte

The Command Byte has three fields, the Address, the

Command, and 2 Data bits, see Figure 7-1. Currently

only one of the data bits is defined (D8). This is for the

Write command.

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 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.

As the Command Byte is being loaded into the device

(on the SDI pin), the device’s SDO pin is driving. The

SDO pin will output high bits for the first six bits of that

command. On the 7th bit, the SDO pin will output the

CMDERR bit state (see Section 7.3 “Error Condi-

tion”). The 8th bit state depends on the the command

selected.

TABLE 7-1:

COMMAND BIT OVERVIEW

FIGURE 7-1:

General SPI Command Formats.

C1:C0 Bit

States

Command

# of Bits

Read Data

16-Bits

Write Data

16-Bits

Increment

8-Bits

Decrement

8-Bits

Memory

Command Byte

Data

Address

Bits

Command

Bits

Memory

16-bit Command

Data

Address

Bits

Command

Bits

0 0 = Write Data

0 1 = INCR

1 0 = DECR

1 1 = Read Data

C C

1 0

Command

Bits

8-bit Command

Command Byte

Data Byte

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