MCP39F511 datasheet(15/62 Pages) MICROCHIP

15 / 62 page

 2015 Microchip Technology Inc.

DS20005393B-page 15

MCP39F511

4.0

COMMUNICATION PROTOCOL

The communication protocol for the MCP39F511

device is based on the Simple Sensor Interface (SSI)

protocol. This protocol is used for point-to-point

communication from a single-host MCU to a

single-slave MCP39F511.

All communication to the device occurs in frames. Each

frame consists of a header byte, the number of bytes in

the frame, command packet (or command packets)

and a checksum. It is important to note that the

maximum number of bytes in either a receive or

transmit frame is 35.

This approach allows for single, secure transmission

from the host processor to the MCP39F511 with either

a single command or multiple commands. No com-

mand in a frame is processed until the entire frame is

complete and the checksum and number of bytes are

validated.

The number of bytes in an individual command packet

depend on the specific command. For example, to set

the instruction pointer, three bytes are needed in the

packet: the command byte and two bytes for the

address you want to set to the pointer. The first byte in

a command packet is always the command byte.

This protocol can also be used to set up transmission

from the MCP39F511 on specific registers. A

predetermined single-wire transmission frame is

defined for one-wire interfaces. The Auto-transmit

mode can be initiated by setting the SINGLE_WIRE bit

in the System Configuration register, allowing for

single-wire communication within the application. See

Section 4.8 “Single-Wire Transmission Mode”

for

more information on this communication.

4.1

Device Responses

After the reception of a communication frame, the

MCP39F511 has three possible responses, which will

be returned with or without data, depending on the

frame received. These responses are either:

• Acknowledge (ACK, 0x06): Frame received with

success, commands understood and commands

executed with success.

• Negative Acknowledge (NAK, 0x15): Frame

received with success, however commands not

executed with success, commands not

understood or some other error in the command

bytes.

• Checksum Fail (CSFAIL, 0x51): Frame received

with success, however the checksum of the frame

did not match the bytes in the frame.

Note:

There is one unique device ID response

which is used to determine which

MCP39FXXX

device

present:

[NAK(0x15) + ID_BYTE]. If the device is

interrogated with 0x5A, i.e. it receives 0x5A

as the first byte instead of the standard

0xA5 first header byte, a special NAK is

returned followed by an ID_BYTE. For the

MCP39F511 the ID_BYTE is 0x01. This

functionality is only present on system ver-

sions 0xFA14 and later.

FIGURE 4-1:

Communication Frame.MCP39F511

Note:

If a custom communication protocol is

desired, please contact a Microchip sales

office.

Header Byte (0xA5) Number of Bytes

Command Packet1 Command Packet2 ...Command Packet n

Checksum

Command

BYTE0

BYTE1 BYTE2 BYTE N

BYTE N

Frame

MCP39F511 Datasheet(PDF) 15 Page - Microchip Technology

MCP39F511 Datasheet(HTML) 15 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62

Datasheet Download

Link URL