MXT1664T3-C2TESSQTP datasheet(51/98 Pages) MICROCHIP

51 / 98 page

MXT1664T3 2.0

 2018 Microchip Technology Inc.

DS40002054A-page 51

10.4.1.1

Command and Response Packets

The command packet has the generic format given in Figure 10-3. The following sections give examples on using the

command to write to the memory map and to read from the memory map.

FIGURE 10-3:

READ/WRITE MEMORY MAP – COMMAND PACKET FORM

In Figure 10-3:

• Rpt ID is the USB report ID used for Object Protocol commands and responses (see Table 10-3 on page 50).

• Command ID is the command ID for the write/read operation (0x51)

• NumWx is the number of data bytes to write to the memory map (may be zero). If the address pointer is being

sent, this must include the size of the address pointer.

• NumRx is the number of data bytes to read from the memory map (may be zero).

• Addr 0 and Addr 1 form the address pointer to the memory map (where necessary; may be zero if not needed).

This is typically an address of an object within the device.

• Data 0 to Data 57 are the bytes of data to be written (in the case of a write). Note that data locations beyond the

number specified by NumWx will be ignored.

The response packet has the generic format given in Figure 10-4.

FIGURE 10-4:

READ/WRITE MEMORY MAP – RESPONSE PACKET FORMAT

In Figure 10-4:

• Status indicates the result of the command:

- 0x00 = read and write completed; read data returned

- 0x04 = write completed; no read data requested

• NumRx is the number of bytes following that have been read from the memory map (in the case of a read). This

will be the same value as NumRx in the command packet.

• Data 0 to Data 60 are the data bytes read from the memory map.

10.4.1.2

Writing To the Device

A write operation cycle to the device consists of sending a packet that contains six header bytes (see Section 10.4.1.1

“Command and Response Packets”). These specify the USB report ID, the Command ID, the number of bytes to read,

the number of bytes to write, and the 16-bit address pointer.

Subsequent bytes in a multibyte transfer form the actual data. These are written to the location of the address pointer,

location of the address pointer +1, location of the address pointer + 2, and so on.

Figure 10-5 shows an example command packet to write four bytes of data to contiguous addresses starting at 0x1234.

FIGURE 10-5:

EXAMPLE OF A FOUR-BYTE WRITE STARTING AT ADDRESS 0x1234

Write Data

(58 Bytes)

Data 57

Data 0

...

0x51

NumWx

Address Pointer

(LSByte, MSByte)

Number of Bytes

to Read/Write

NumRx

Addr 0

Addr 1

Rpt ID

Command

Read Data

(61 Bytes)

Data 60

Rpt ID

Status

Number of

Bytes Read

Success/

Failure

NumRx

Data 0

...

Write Data

(4 Bytes)

0x51

0x06

Number

of Bytes

to Write

0x00

0x34

0x12

0x96

0x9B

0xA0

0xA5

Address Pointer

(LSByte, MSByte)

Number

of Bytes

to Read

Command

Rpt ID

Unused Bytes

(54 bytes)

0x00

...

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