MCP39F511A datasheet(16/68 Pages) MICROCHIP

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MCP39F511A

DS20006044A-page 16

 2018 Microchip Technology Inc.

4.2

Checksum

The checksum is generated using simple byte addition

and taking the modules to find the remainder after

dividing the sum of the entire frame by 256. This oper-

ation is done to obtain an 8-bit checksum. All the bytes

of the frame are included in the checksum, including

the header byte and the number of bytes. If a frame

includes multiple command packets, none of the com-

mands will be issued if the frame checksum fails. In this

instance, the MCP39F511A device will respond with a

CSFAIL response of 0x51.

On commands that are requesting data back from the

MCP39F511A device, the frame and checksum are

created in the same way, with the header byte becom-

ing an Acknowledge (0x06). Communication examples

are given in Section 4.5 “Example Communication

Frames and MCP39F511A Responses”

4.3

UART Settings

The default baud rate is 9.6 kbps and can be changed

using the UART bits in the System Configuration

. Note that the baud rate is changed at

system power-up, so when changing the baud rate, a

Save

Flash

command followed by a power-on

cycle is required. The UART operates in 8-bit mode,

plus one Start bit and one Stop bit, for a total of 10 bits

per byte, as shown in Figure 4-2.

FIGURE 4-2:

UART Transmission, N-8-1.

IDLE

START

IDLE

STOP

D0 D1

D3 D4

D5 D6 D7

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