SCN68652 datasheet(16/28 Pages) PHILIPS

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Philips Semiconductors

Product specification

SCN2652/SCN68652

Multi-protocol communications controller (MPCC)

1995 May 01

Table 8.

Receiver Data/Status Register (RDSR)–(Read Only)

BIT

NAME

MODE

FUNCTION

00–07

RxDB

BOP/BCP

Receiver data buffer. Contains assembled characters from the RxSR. If VRC is specified, the

parity bit is stripped.

RSOM

BOP

Receiver start of message = 1 when a FLAG followed by a non-FLAG has been received and

the latter character matches the secondary station if SAM = 1. RxA will be asserted when

RSOM = 1. RSOM resets itself after one character time and has no affect on RxSA.

REOM

BOP

Receiver end of message = 1 when the closing FLAG is detected and the last data character

is loaded into RxDB or when an ABORT/GA character is received. REOM is cleared on

reading RDSRH, reset operation, or dropping of RxE.

RAB/GA

BOP

Received ABORT or GA character = 1 when the receiver senses an ABORT character if

SS/GA = 0 or a GA character if SS/GA = 1. RAB/GA is cleared on reading RDSRH, reset

operation, or dropping of RxE. A received abort does not set RxDA.

ROR

BOP/BCP

Receiver overrun = 1 indicates the processor has not read last character in the RxDB within

one character time + 1/2 RxC period after RxDA is asserted. Subsequent characters will be

lost. ROR is cleared on reading RDSRH, reset operation, or dropping of RxE.

12–14

ABC

BOP

Assembled bit count. Specifies the number of bits in the last received data character of a

message and should be examined by the processor when REOM = 1(RxDA and RxSA

asserted). ABC = 0 indicates the message was terminated (by a flag or GA) on a character

boundary as specified by PCR8–10. Otherwise, ABC = number of bits in the last data

character. ABC is cleared when RDSRH is read, reset operation, or dropping RxE. The

residual character is right justified inRDSRL.

RERR

BOP/BCP

Receiver error indicator should be examined by the processor when REOm = 1 in BOP, or

when the processor determines the last data character of the message in BCP with CRC or

when RxSA is set in BCP with VRC.

CRC–CCITT preset to 1’s/0’s as specified by PCSAR8–10:

RERR = 1 indicates FCS error (CRC

≠ F0B8 or ≠ 0)

RERR = 0 indicates FCS received correctly (CRC = F0B8 or = 0)

CRC–16 preset to 0’s on 8-bit characters specified by PSCAR8–10:

RERR = 1 indicates CRC–16 received correctly (CRC = 0).

RERR = 0 indicates CRC–16 error (CRC

≠0)

VRC specified by PCSAR8–10:

RERR = 1 indicates VRC error

RERR = 0 indicates VRC is correct.

DC ELECTRICAL CHARACTERISTICS1, 2

PARAMETER

TEST CONDITIONS

LIMITS

UNIT

PARAMETER

TEST CONDITIONS

Min

Typ

Max

UNIT

Input voltage

VIL

Low

0.8

VIH

High

2.0

Output voltage

VOL

Low

IOL = 1.6mA

0.4

VOH

High

IOH = –100µA

2.4

ICC

Power supply current

VCC = 5.25V, TA = 0°C

150

Leakage current

IIL

Input

VIN = 0 to 5.25V

µA

IOL

Output

VOUT = 0 to 5.25V

Capacitance

CIN

Input

VIN = 0V, f = 1MHz

COUT

Output

VOUT = 0V, f = 1MHz

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