SENA HD1200 - Manual (Page 34)

Starter Kit and User Manual for the HelloDevice 1200
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The address of 2 Kbytes of Dual-Port RAM is from 0x000 to 0x7EF. So you should consider this scope in
designing communication interface between your system and the HelloDevice.
6.2.1 Reading a Dual-Port RAM
To read specified area of the HelloDevice Dual-Port RAM from your PC, you should send corresponding
commands into the HelloDevice from socket interface program of PC. the HelloDevice will reply to this
command and returns corresponding response. The Read command and corresponding response are summarized
in table 6.3. As it is shown as the table 6.3, the maximum readable data length is limited to 1450(=0x5AA) byte.
This limitation is from the fact that maximum number of bytes that can be sent in Ethernet frame is 1500 bytes
including header lengths of TCP/IP.
Number of Byte Command
1 2 3 4 5 …
Read command 0x77 Dual-Port RAM
Address
(0x0000 ~ 0x07EF) Data length
(0x000 ~ 0x05AA)
Read response Address of
Response data Length of
Response data Data value of the
specified size
Table 6.3. the HelloDevice Dual-Port RAM Read protocol
This is the command that will read specified address of HelloDevice Dual-Port RAM and will be followed by the
corresponding response.
Let’s say that you want to read 4 bytes of data, the address of which starts from 0x10. If the current data of that
address is 0x12345678, it will be displayed like table 6.4.
0x77 0x00 0x10 0x00 0x04
Command Address Length
0x00 0x10 0x00 0x04 0x12 0x34 0x56 0x78
Address Length Data
Table 6.4. Example of Dual-Port RAM Read command/response
6.2.2 Writing a Dual-Port RAM
This command is used to change specified length of data in a specified location of Dual-Port RAM. It does not
require any response from the HelloDevice. The maximum writing data length is also limited to 249(=0x0F9)