Philips Semiconductors

Product specification

SCN2652/SCN68652

Multi-protocol communications controller (MPCC)

1995 May 01

14

Table 6.

Parameter Control SYNC/Address Register (PCSAR)–(R/W)

BIT

NAME

MODE

FUNCTION

00–07

S/AR

BOP

SYNC/address register. Contains the secondary station address if the MPCC is a secondary

station. The contents of this register is compared with the first received non-FLAG character

to determine if the message is meant for this station.

BCP

SYNC character is loaded into this register by the processor. It is used for receive and

transmit bit synchronization with bit length specified by RxCL and TxCL.

08–10

ECM

BOP/BCP

Error Control Mode

10

9

8

Suggested Mode

Char. length

CRC–CCITT preset to 1’s

0

0

0

BOP

1–8

CRC–CCITT preset to 0’s

0

0

1

BCP

8

Not used

0

1

0

–––

CRC–16 preset to 0’s

0

1

1

BCP

8

VRC odd

1

0

0

BCP

5–7

VRC even

1

0

1

BCP

5–7

Not used

1

1

0

–––

No error control

1

1

1

BCP/BOP

5–8

ECM should be loaded by the processor during initialization or when both data paths are idle.

11

IDLE

Determines line fill character to be used if transmitter underrun occurs (TxU asserted and

TERR set) and transmission of special characters for BOP/BCP.

BOP

IDLE = 0, transmit ABORT characters during underrun and when TABORT = 1.

IDLE = 1, transmit FLAG characters during underrun and when TABORT = 1.

BCP

IDLE = 0 transmit initial SYNC characters and underrun line fill characters from theS/AR.

IDLE = 1 transmit initial SYNC characters from TxDB and marks TxSO during underrun.

12

SAM

BOP

Secondary Address Mode = 1 if the MPCC is a secondary station. This facilitates automatic

recognition of the received secondary station address. When transmitting, the processor must

load the secondary address into TxDB.

SAM = 0 inhibits the received secondary address comparison which serves to activate the

receiver after the first non-FLAG character has been received.

13

SS/GA

Strip SYNC/Go Ahead. Operation depends on mode.

BOP

SS/GA = 1 is used for loop mode only and enables GA detection. When a GA is detected as a

closing character, REOM and RAB/GA will be set and the processor should terminate the

repeater function. SS/GA = 0 is the normal mode which enables ABORT detection. It causes

the receiver to terminate the frame upon detection of an ABORT or FLAG.

BCP

SS/GA = 1, causes the receiver to strip SYNC’s immediately following the first two SYNC’s

detected. SYNC’s in the middle of a message will not be stripped. SS/GA = 0, presents any

SYNC’s after the initial two SYNC’s to the processor.

14

PROTO

Determines MPCC Protocol mode

BOP

PROTO = 0

BCP

PROTO = 1

15

APA

BOP

All parties address. If this bit is set, the receiver data path is enabled by an address field of

‘11111111’ as well as the normal secondary station address.