COM20019I-HD View Datasheet(PDF) - SMSC -> Microchip

Part Name

Description

MFG CO.

COM20019I-HD

Cost Competitive ARCNET (ANSI 878.1) Controller with 2K x 8 On-Chip RAM

SMSC -> Microchip 

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Low Cost ARCNET (ANSI 878.1) Controller with 2K x 8 On-Board RAM

ƒ An ALERT BURST

ƒ An SOH (Start Of Header--ASCII code 01H)

ƒ An SID (Source ID) character

ƒ Two (repeated) DID (Destination ID) characters

ƒ A single COUNT character which is the 2's complement of the number of data bytes to follow if a

short packet is sent, or 00H followed by a COUNT character if a long packet is sent.

ƒ N data bytes where COUNT = 256-N (or 512-N for a long packet)

ƒ Two CRC (Cyclic Redundancy Check) characters. The CRC polynomial used is: X16 + X15 + X2 + 1.

ALERT

SOH SID DID DID COUNT data

BURST

data CRC CRC

4.6.4 Acknowledgements

An Acknowledgement is used to acknowledge reception of a packet or as an affirmative response to FREE

BUFFER ENQUIRIES and is sent by the following sequence:

ƒ An ALERT BURST

ƒ An ACK (ACKnowledgement--ASCII code 86H) character

ALERT BURST

ACK

4.6.5 Negative Acknowledgements

A Negative Acknowledgement is used as a negative response to FREE BUFFER ENQUIRIES and is sent

by the following sequence:

ƒ An ALERT BURST

ƒ A NAK (Negative Acknowledgement--ASCII code 15H) character

ALERT BURST

NAK

Rev. 04-15-05

Page 14

DATASHEET

SMSC COM20019I

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