MPR03X

Sensors

6

Freescale Semiconductor

2.3.6

Message Format for Writing the MPR03X

A write to the MPR03X comprises the transmission of the MPR03X’s keyscan slave address with the R/W bit set to 0, followed

by at least one byte of information. The first byte of information is the command byte. The command byte determines which

register of the MPR03X is to be written by the next byte, if received. If a STOP condition is detected after the command byte is

received, the MPR03X takes no further action (Figure 10) beyond storing the command byte. Any bytes received after the

command byte are data bytes.

Figure 10. Command Byte Received

Any bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MPR03X

Figure 11. Command and Single Data Byte Received

If multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequent

MPR03X internal registers because the command byte address generally auto-increments (Section 2.4).

2.3.7

Message Format for Reading the MPR03X

MPR03X is read using MPR03X's internally stored register address as address pointer, the same way the stored register address

is used as address pointer for a write. The pointer generally auto-increments after each data byte is read using the same rules

as for a write (Table 5). Thus, a read is initiated by first configuring MPR03X's register address by performing a write (Figure 10)

followed by a repeated start. The master can now read 'n' consecutive bytes from MPR03X, with first data byte being read from

the register addressed by the initialized register address.

Figure 12. Reading MPR03X

SAA

P

0

SLAVE ADDRESS

COMMAND BYTE

acknowledge from MPR03X

R/W

acknowledge from MPR3X

D15 D14 D13 D12 D11 D10

D9

D8

Commandbyte is storedonreceipt ofSTOP condition

SA

AA

P

0

SLAVE ADDRESS

COMMAND BYTE

DATA BYTE

acknowledge from MPR03X

R/W

1byte

auto-increment memory

word address

D15 D14 D13 D12 D11 D10 D9 D8

D1 D0

D3 D2

D5 D4

D7 D6

Howcommand byte and data byte

map into MPR03X's registers

acknowledge from

MPR03X

acknowledge from

MPR03X

SAA P

1

SLAVE ADDRESS

DATA BYTE

R/W

n bytes

auto-increment memory

word address

D1 D0

D3 D2

D5 D4

D7 D6

acknowledge from MPR03X

acknowledge from master