SCN68652 datasheet(5/28 Pages) PHILIPS

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Philips Semiconductors

Product specification

SCN2652/SCN68652

Multi-protocol communications controller (MPCC)

1995 May 01

Table 1.

REGISTERS

NO. OF BITS

DESCRIPTION*

Addressable

PCSAR

Parameter control sync/

address register

PCSARH and PCR contain parameters common to the

receiver and transmitter. PCSARL contains a programmable

SYNC character (BCP) or secondary station address (BOP).

PCR

Parameter control register

RDSRH contains receiver status information.

RDSR

Receive data/status register

RDSRL = RxDB contains the received assembled character.

TDSR

Transmit data/status register

TDSRH contains transmitter command and status

information. TDSRL = TxDB contains the character to be

transmitted

Non-Addressable

CCSR

Control character shift register

HSR

Holding shift register

RxSR

Receiver shift register

These registers are used for character assembly (CSSR

TxSR

Transmitter shift register

These registers are used for character assembly (CSSR,

HSR, RxSR), disassembly (TxSR), and CRC

RxCRC

Receiver CRC accumulation

,),

y (

accumulation/generation (RxCRC, TxCRC).

TxCRC

Transmitter CRC generation

NOTES:

*H = High byte – bits 15–8

L = Low byte – bits 7–0

Table 2.

Error Control

CHARACTER

DESCRIPTION

FCS

Frame check sequence is transmitted/received

as 16 bits following the last data character of a

BOP message. The divisor is usually

CRC–CCITT (X16 + X12 + X5 + 1) with dividend

preset to 1’s but can be other wise determined

by ECM. The inverted remainder is transmitter as

the FCS.

BCC

Block check character is transmitted/received as

two successive characters following the last data

character of a BCP message. The polynomial is

CRC–16 (X16 + X15 + X2 + 1) or CRC–CCITT

with dividend preset to 0’s (as specified by

ECM). The true remainder is transmitted as the

BCC.

Table 3.

Special Characters

OPERATION

BIT PATTERN

FUNCTION

BOP

FLAG

01111110

Frame message

ABORT

11111111 generation

Terminate communication

01111111 detection

01111111

Terminate loop mode

repeater function

Address

(PCSARL)1

Secondary station address

BCP

SYNC

(PCSARL) or

(TxDB)2 generation

Character synchronization

NOTES:

1. ( ) = contents of.

2. For IDLE = 0 or 1 respectively.

APA

PCSAR

PCR

RDSR

TDSR

PROTO

SS/GA

SAM

IDLE

E C M

S/AR

32 10

TxCL

RxCL

R x

RERR

A B C

ROR

RAB/

REOM

RxDB

RSOM

TERR

NOT DEFINED

TGA

TABORT

TEOM

TxDB

TSOM

NOTE:

Refer to Register Formats for mnemonics and description.

SD00059

Figure 3. Short Form Register Bit Formats

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