Note 1: A status bit is set when its corresponding condition is true and is cleared when the condition is false.

Note 2: Aninterruptflag(exceptthePOR_Flag)issetonlywhenitsinterruptenablebitistrueanditscorrespondingstatusbitgoes

fromalogiczerostatetologiconestate.Theflagcanonlybeclearedbywritingittoalogiczero.Ifthestatusbitistrue

when the flag enable is set or when the flag is cleared, the flag remains cleared until the status bit transitions from a logic

zerostatetoalogiconestate.

Note 3: Ifanyinterruptflag(exceptthePOR_Flag)isset,thentheINT pin is asserted (active low).

Register Table (continued)

RX_BYTE REGISTER

ADDRESS

BITS

DEFAULT

NAME

DESCRIPTION

0x19 (Read)

7:3

00000

Reserved

Alwaysreadslogiczero.

2

0

First_Byte

ThebyteatlocationRX_RD_Pointeristhefirstdata

byte in a message (the corresponding character was

preceded by preamble character).

1

0

Byte_Error

ThebyteatlocationRX_RD_Pointermaycontain

an error (the corresponding character contained a

Manchester and/or parity error). This bit drives the

RX_Errorinterrupt.

0

0

Last_Byte

ThebyteatlocationRX_RD_Pointeristhelastbytein

a message (the corresponding character was a stop

character and was stored as a null byte).

RX_SPACE REGISTER

0x1B (Read)

7:0

00111110

RX_Space[7:0]

Numberofavailablebytesinthereceivebuffer.

Defaultis62bytes(3Eh).

TX_QUEUE_SELECTS REGISTER

0x95 (Read)

7:4

0000

Reserved

Alwaysreadslogiczero.

3:2

00

TX_Q[1:0]

TransmitQueueSelect:Addressesoneoffour

queuesinthetransmitbufferthattheUARThas

selected for message transmission (sending).

1:0

00

LD_Q[1:0]

LoadQueueSelect:Addressesoneoffourqueues

inthetransmitbufferthatthehosthasselectedfor

message loading (writing).

RX_READ_POINTER REGISTER

0x97 (Read)

7:0

00h

RX_RD_Pointer[7:0]

ReceiveBufferReadPointer:Thelocationinthe

receivebufferthatthehostistoread.TheUART

automatically increments this pointer.

RX_WRITE_POINTER REGISTER

0x99 (Read)

7:0

01h

RX_WR_Pointer[7:0]

ReceiveBufferWritePointer:Thelocationinthe

receivebufferthatiswrittenbytheUARTasit

receives data.

RX_NEXT_MESSAGE REGISTER

0x9B (Read)

7:0

00h

RX_NXT_MSG_

Pointer[7:0]

ReceiveBufferNextMessagePointer:Thestartof

thenextunreadmessageinthereceivebuffer.The

RX_RD_Pointerisloadedwiththisvaluebythe

RD_NXT_MSGSPItransaction.

Maxim Integrated │ 31

MAX17841B

Automotive SPI Communication Interface (ASCI)

www.maximintegrated.com