MAX17841B datasheet(23/33 Pages) MAXIM

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ThehostshouldalsosettheASCI’sRX_Error_INT_Enable

bit. If, in the course of reading the receive buffer, the ASCI

setstheRX_Error_INT_Flag,itmeansthattheUARThad

detected a Manchester and/or parity error in at least one

of the received characters in the message. Because

Manchester and parity errors can be introduced anywhere

intheUARTdatastream,theerrorsdenotedbytheRX_

Error_INT_Flagarenotnecessarilyreflectedintheerror-

checking bytes returned by the slave device(s). Therefore,

the host should check and clear this flag after (but not

before) reading each message in the receive buffer.

Corrupted or Missing Stop Character

If a stop character is corrupted or missing, there is no data

loss because the message is still framed either by a sub-

sequent valid stop character (that is automatically sent in

Keep-Alivemode)orbythepreambleofthenextUARTmes-

sage. A corrupted stop character can be interpreted as a data

character and would be stored as such in error. In this case,

if a valid stop character is eventually received before the next

preamble, the message length is one byte too long. The host

should check for this condition by computing the received

message length and comparing it to the expected message

length.

Before reading the next message, the host should also check

theRX_Byteregistertoverifythatthelastcharacterreceived

was a valid stop character, in which case all of the following

are true:

1) The last byte in the message is a null byte (00h).

2) TheLast_Bytebitisset.

3) TheByte_Errorbitiscleared.

IfastopcharacterwasnotreceivedthentheLast_Byte

bit is not set.

Unintended Preamble

The presence of an unintended preamble in the middle

of a message creates an unintended message in the

receive buffer. If the unintended preamble is the result of a

corrupted data character within a message, then the mes-

sage is prematurely terminated and a second, unexpected

message is created. This event can be detected by

comparing the number of received bytes in the message

to the expected number.

Unintended Stop Character

The presence of an unintended stop character prema-

turely terminates the message. This is detected by com-

paring the number of received bytes in the message to the

expected number.

UART Physical Layer

Single-Ended Mode

By default, UART ports are configured for differential

communication. For single-ended operation, the host can

settheSingle_Ended_Modeconfigurationbit.Thismode

enables the UART to receive a single-ended signal by

shiftingtheinputthresholdnegativesothatzerodifferen-

tial voltage is a logic one. The RXP input is connected to

ground and the RXN input receives the inverted signal,

just as it does for differential mode. In this mode, the Tx

port operates the same as in differential mode.

Figure 13. Single-Ended Mode

1.5kΩ

RXP

RXN

GNDL

15pF

Maxim Integrated │ 23

MAX17841B

Automotive SPI Communication Interface (ASCI)

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