CS5490 datasheet(25/56 Pages) APEX

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CS5490

DS982F2

6.1.3 Checksum

To improve the communication reliability on the serial

interface, the CS5490 provides a checksum mechanism

on transmitted and received signals. Checksum is

disabled by default but can be enabled by setting the

appropriate bit in the SerialCtrl register. When enabled,

both host and CS5490 are expected to send one

additional checksum byte after the normal command

byte and applicable 3-byte register data have been

transmitted.

The checksum is calculated by subtracting each

transmit byte from 0xFF. Any overflow is truncated and

the result wraps. The CS5490 executes the command

only if the checksum transmitted by the host matches

the checksum calculated locally. Otherwise, it sets a

status bit (RX_CSUM_ERR in Status0 register), ignores

the command, and clears the serial interface in

preparation for the next transmission.

Figure 18. Byte Sequence for Checksum

6.1.4 Serial Time Out

In case a transaction from the host is not completed (for

example, a data byte is missing in a register write), a

time out circuit will reset the interface after 128ms. This

will require that each byte be sent from the host within

128ms of the previous byte.

Checksum

Page Select Cmd.

CHECKSUM

DATA

CHECKSUM

Read Cmd.

DATA

CHECKSUM

Write Cmd.

Checksum

Instruction

Page Select

Instruction

Read Command

Write Command

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