UM0934 datasheet(38/113 Pages) STMICROELECTRONICS

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Host interface

UM0934

38/113

Doc ID 17389 Rev 2

As described in Section 2.2, the ST7570 protocol stack implemented in compliance with [2]

can be accessed at the physical layer (PHY mode) or at the MAC layer (MAC mode).

Several commands of the host interface may present a different format and behavior

according to the selected mode.

Local frames

The format of the frame used in the local communication between the ST7570 and the

external host is graphically represented in Figure 15:

Figure 15.

Local frame format

The frame fields are described in Table 10:

Byte endianness for fields (data and checksum) with a length greater than one byte is:

●

Data field: structured in sub-fields in accordance with command code specifications

described in 5.3. Sub-fields with a length greater than one byte are sent LSByte first

unless otherwise specified

●

Checksum field: is sent LSByte first.

Table 10.

Local frame format

Field

Byte length

Value

Description

STX

02h

Start of text delimiter

Length

3..250 Byte length of fields: command + data + checksum

Command code

0..FFh Command code

Data

0..247

Data field (247 byte max)

Checksum

The checksum of the local frame is the result of the addition

of the elements of the frame, from length up to the last data

byte, or up to the command byte if there is no data byte.

STX

Length

Command

Code

DATA

Checksum

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