Applications information, Table 4. autoincrement rules – Rainbow Electronics MAX7360 User Manual

Page 16

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C-Interfaced Key-Switch Controller and LED

Driver/GPIOs with Integrated ESD Protection

MAX7360

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transaction, either read or write, if SCL low exceeds

20ms. After a bus timeout, the MAX7360 waits for a valid

START condition before responding to a consecutive

transmission. This feature can be enabled or disabled

under user control by writing to the configuration register

(Table 8 in the Register Tables section).

Message Format for Writing

the Key-Scan Controller

A write to the MAX7360 comprises the transmission of the

slave address with the R/W bit set to zero, followed by at

least 1 byte of information. The first byte of information

is the command byte. The command byte determines

which register of the MAX7360 is to be written by the next

byte, if received. If a STOP condition is detected after the

command byte is received, the MAX7360 takes no further

action (Figure 7) beyond storing the command byte.
Any bytes received after the command byte are data bytes.

The first data byte goes into the internal register of the

MAX7360 selected by the command byte (Figure 8).
If multiple data bytes are transmitted before a STOP condition

is detected, these bytes are generally stored in subsequent

MAX7360 internal registers, because the command byte

address generally autoincrements (Table 4).

Message Format for Reading

the Key-Scan Controller

The MAX7360 is read using the internally stored

command byte as an address pointer, the same way the

stored command byte is used as an address pointer for

a write. The pointer generally autoincrements after each

data byte is read using the same rules as for a write

(Table 4). Thus, a read is initiated by first configuring the

MAX7360’s command byte by performing a write (Figure

6). The master can now read n consecutive bytes from

the MAX7360, with the first data byte being read from

the register addressed by the initialized command byte.

When performing read-after-write verification, remember

to reset the command byte’s address, because the stored

command byte address is generally autoincremented

after the write (Figure 9, Table 4).

Operation with Multiple Masters

When the MAX7360 is operated on a 2-wire interface with

multiple masters, a master reading the MAX7360 uses a

repeated start between the write that sets the MAX7360’s

address pointer, and the read(s) that takes the data

from the location(s). This is because it is possible for

master 2 to take over the bus after master 1 has set up

the MAX7360’s address pointer, but before master 1

has read the data. If master 2 subsequently resets the

MAX7360’s address pointer, master 1’s read can be from

an unexpected location.

Command Address Autoincrementing

Address autoincrementing allows the MAX7360 to be

configured with fewer transmissions by minimizing the

number of times the command address needs to be sent.

The command address stored in the MAX7360 generally

increments after each data byte is written or read (Table

4). Autoincrement only works when doing a multiburst

read or write.

Applications Information

Reset from I

After a catastrophic event such as ESD discharge or

microcontroller reset, use bit D7 of the configuration

state (the key-switch register values and FIFO remain

unaffected). Use bit D4 of the GPIO global configuration

Figure 9. N Data Bytes Received

Table 4. Autoincrement Rules

ADDRESS

CODE (hex)

AUTOINCREMENT

ADDRESS (hex)

Keys FIFO

0x00

Autoshutdown

0x06

0x00

All other key switch

0x01 to 0x05

Addr + 0x01

All other GPIO

0x40 to 0x5F

Addr + 0x01

SLAVE ADDRESS

COMMAND BYTE

DATA BYTE

N BYTES

AUTOINCREMENT

COMMAND BYTE ADDRESS

ACKNOWLEDGE FROM MAX7360

R/W

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