Matrix-orbital GLK240128-25 Bedienungsanleitung PDF herunterladen (Seite 55)

50 Command Summary

send a 128 byte block of data followed by that blocks high and low CRC16 bytes. The display then

performs a CRC check on the data receive and ACKs if it matches that which was sent. Transfer

continues with a block count and continues in this way until the end of file is reached. Files may be

padded with 255 values to reach an even multiple of 128 bytes in size, but the download command will

always report true size. Once the end of the upload file is reached, the host should transmit a single end

of transmission byte. If the end of file is expected, the display will ACK one last time.

Table 42: XModem File Upload Protocol

Host

Display

Comments

254

Command Prefix

220

XModem Upload Command

133

Command Byte One

Command Byte Two

Command Byte Three

File ID LSB

File ID MSB

File Type

Size LSB

Size

Size MSB

C (If file fits)

Start of Header

128

Block Count

127

Inverted Block Count (255-Count)

<128 B>

128 Byte Data Block

*CRC MSB

*CRC LSB

ACK (NAK if counts don’t match)

…

End of Transmission

ACK (NAK if EOT is not expected)

Table 43: XModem File Download Protocol

Host

Display

Comments

254

Command Prefix

221

XModem Download Command

133

Command Byte One

Command Byte Two

Command Byte Three

File ID LSB

File ID MSB

File Type

Size LSB (NAK if not found)

Size

Size MSB

Start of Header

128

Block Count

127

Inverted Block Count (255-Count)

<128 B>

128 Byte Data Block

*CRC MSB

*CRC LSB

ACK (NAK if counts don’t match)

…

End of Transmission

ACK (NAK if EOT is not expected)

Table 44: XModem Message Bytes

Value

Action

Description

Start of Header

Begin upload transfer

End of Transmission

End completed upload transfer

Acknowledged

Transfer successful, upload continues

Not Acknowledged

Transfer failed, upload aborted

Confirmation that file will fit

*Note: CRC bytes are calculated using the XMODEM CRC-CCITT algorithm available at:

http://www.matrixorbital.ca/appnotes/XModem/ymodem.txt.

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