MCP8024 datasheet(24/46 Pages) MICROCHIP

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MCP8024

DS20005228A-page 24

 2013 Microchip Technology Inc.

FIGURE 4-2:

DE2 PACKET FORMAT.

FIGURE 4-3:

DE2 PACKET TIMING.

4.5.4

MESSAGING INTERFACE

A command byte will always have the most significant

bit 7 (msb) set to ‘1’. Bits 6 and 5 are reserved for future

use and should be set to ‘0’. Bits 4:0 are used for com-

mands. That allows for 32 possible commands.

4.5.4.1

Host to MCP8024

Messages sent from the host to the MCP8024 device

consist of either one or two eight-bit bytes. The first

byte transmitted is the command byte. The second

byte transmitted, if required, is the data for the com-

mand.

4.5.4.2

MCP8024 to Host

A solicited response byte from the MCP8024 device

will always echo the command byte with bit 7 set to ‘0’

(Response) and with bit 6 set to ‘1’ for Acknowledged

(ACK) or ‘0’ for Not Acknowledged (NACK). The sec-

ond byte, if required, will be the data for the host com-

mand. Any command that causes an error or is not

supported will receive a NACK response.

The MCP8024 may send unsolicited command

messages to the host controller. All messages to the

host controller do not require a response from the host

controller.

4.5.4.3

Messages

4.5.4.3.1 SET_CFG_0

There is a SET_CFG_0 message that is sent by the

host to the MCP8024 device to configure the device.

The SET_CFG_0 message may be sent to the device

at any time. The host is responsible for making sure

the system is in a state that will not be compromised

by sending the SET_CFG_0 message. The SET_CF-

G_0

message format is indicated in Table 4-2. The

response is indicated in Table 4-3.

4.5.4.3.2 GET_CFG_0

There is a GET_CFG_0 message that is sent by the

host to the MCP8024 device to retrieve the device

configuration register. The GET_CFG_0 message for-

mat is indicated in Table 4-2. The response is indi-

cated in Table 4-3.

4.5.4.3.3 STATUS_0/1

There is a STATUS_0/1 message that is sent by the

host to the MCP8024 device to retrieve the device

STATUS register. The STATUS_0/1 message may

also be sent to the host by the MCP8024 device to

inform the host of status changes. The STATUS_0/1

message format is indicated in Table 4-2. The

response is indicated in Table 4-3.

STOP

START

DE2

Message Format

STOP

START

TSTART = 1.5T – uncertainty on start

Detection (worse case: 2x TS)

TS = T/16 (oversampled bit-cell period)

Receiver samples the incoming data

using x16 baud rate clock

Sample incoming data

at the bit-cell center

TSTART

T = 1/Baud Rate (bit-cell period)

Detect start bit by sensing

transition from logic 1 to logic 0

(worst

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