mpr084 Freescale Semiconductor, Inc, mpr084 Datasheet - Page 7

• Manufacturer Part Number: mpr084
• Description: Proximity Capacitive Touch Sensor Controller
• Manufacturer: Freescale Semiconductor, Inc

Sensors
Freescale Semiconductor
2.3.5 The Slave Address
The MPR084 has a 7-bit long slave address
is low for a write command and high for a read command.
The MPR084 monitors the bus continuously, waiting for a START condition followed by its slave address. When a MPR084
recognizes its slave address, it acknowledges and is then ready for continued communication.
2.3.6
A write to the MPR084 comprises the transmission of the MPR084’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 MPR084 is to be written by the next byte, if received. If a STOP condition is detected after the command byte is
received, then the MPR084 takes no further action
command byte are data bytes.
Any bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MPR084
selected by the command byte
If multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequent
MPR084 internal registers because the command byte address generally auto-increments
2.3.7 Message Format for Reading the MPR084
The MPR084 is read using the MPR084’s internally stored command byte as address pointer, the same way the stored command
byte 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
(Figure
addressed by the initialized command byte.
S
S
12). The master can now read ‘n’ consecutive bytes from the MPR084, with the first data byte being read from the register
Message Format for Writing the MPR084
Command byte is stored on receipt ofSTOP condition
SLAVE ADDRESS
How command byte and data byte
(Section
acknowledge from MPR084
map into MPR084's registers
SLAVE ADDRESS
6.4.1). Thus, a read is initiated by first configuring the MPR084’s command byte by performing a write
R/W
acknowledge from MPR084
(Figure
Figure 11. Command and Single Data Byte Received
0
11).
A
Figure 9. Slave Address Transaction
D15 D14 D13 D12 D11 D10 D9
Figure 10. Command Byte Received
(Figure
R/W
Slave address: 0x5C
(Figure
9). The bit following the 7-bit slave address (bit eight) is the R/W bit, which
0
COMMAND BYTE
A
10) beyond storing the command byte. Any bytes received after the
acknowledge from
D7
MPR084
D6
D8
D5
COMMAND BYTE
A
D4
D7
acknowledge from MPR084
D6
D3
(Section
D5
DATA BYTE
D2
D4
1 byte
2.4).
D3
D1
acknowledge from
D2
auto-increment memory
D0
MPR084
D1
word address
A
D0
A
MPR084
P
P
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