COMMUNICATION PROTOCOL

Copyright Semtech 1997-2001

DOC5-SPI-DS-117

www.semtech.com

11

There are eight commands that may be sent from the UR5HCSPI to the host, and ten commands that may be sent

from the host to the UR5HCSPI.

Each command from UR5HCSPI to the host is composed of a sequence of codes. All commands start with

<CONTROL> code (80H) and end with LRC code (see the description of the LRC calculation on page 12).

Command details are listed below.

Commands to the Host - Summary

Command Name

Code

Description

Initialize Request

AOH

Sent to the host when the data buffer is full

Initialize Complete

A1H

Issued upon completion of the “Initialize” command issued by the host

Heartbeat Response

A2H

Response to “Heartbeat Request” issued by the host

Identification Response

F2H

Response to “Identification Request” issued by the host

LED Status Report

A3H

Response to “LED Status Request”

Resend Request

A5H

Issued upon error during the reception of a packet

Initialize Request

<CONTROL>

80H

<INIT>

A0H

<LRC>

20H

The UR5HCSPI will send the Initialize Request Command to the host when

its data buffer is full.

Initialization Complete

<CONTROL>

80H

<INIT COMPLETE>

A1H

<LRC>

21H

The UR5HCSPI wil send the Initialize Complete Report to the host when it

finishes the initialization caused by Initialize Command from the host.

Heartbeat Response

<CONTROL>

80H

<ONLINE>

A2H

<LRC>

22H

The UR5HCSPI will send the Heartbeat Response to the host when it

receives the Heartbeat Request Command from the host.

Identification Response

<CONTROL>

80H

<ID>

F2H

<Vendor>

02H

--- USAR

<Revision>

08H

--- Rev 0.8A

<Switch>

00H

.

<LRC>

7EH

The UR5HCSPI will send the Identification Response to the host when it

receives the Identification Request Command from the host.

The LRC is calculated for the

whole packet, including the

Command Code and the

Command Prefix. The LRC is

calculated by first taking the

bitwise exclusive OR of all bytes

from the message. If the most

significant bit (MSB) of the LRC is

set, the LRC is modified by

clearing the MSB and changing the

state of the next most significant

bit. Thus, the Packet Check Byte

will never consist of a valid LRC

with the most significant bit set.

LRC CALCULATION

COMMANDS TO THE HOST ANALYTICALLY