ARF868 Radio Modems - User guide version V1.8.1
24
Page
of 26
To trigger this procedure the monitoring equipment must transmit, on the serial link, the character: <U> (see § 4.1 self-detection command).
After correct execution of the self-detection command, reading register S210 (ATS210 ?) will return the UART data rate value identified in the
table (value 3 to 7). It will be memorised on recognition of the AT&W command.
Note2
: in the absence of any other special request, the modem internal switches (factory settings) are set to the auto mode (identical to the
S215 Fisher position = 4).
Note3
: the UART data rate should be chosen as close as possible to the radio data rate.
This is to limit the use of the buffer memory zone and activation of the RTC/CTS UART data rate control signals. E.g. 1: for a radio data rate of
57.6Kbps (S254=8), the choice of UART data rate of 57.6Kbps (S210=6) would be ideal. E.g. 2: For a UART data rate of 9.6Kbps (S210=3), the
radio data rate of 9.6Kbps(S254= 3) is the best possible choice.
If it is not possible to bring the UART and Radio data rates close together the 1024 octet buffer memory will compensate for the differences in
speed, provided this difference is not significant and/or the size of the data for transmission is limited.
In all other cases, only the use of the UART data rate control (S216=1) enables the integrity of the data transmitted to be guaranteed.
Note4
: the default choice of manual exiting from the mode is suitable for use during development, when the user needs to maintain control
over the exit from the command mode.
Programming of a timeout is recommended for use in operation, to enable an automatic return by the modem into the communication mode if a
character chain in the data flow is accidentally assimilated to a request for entry into the command mode.
Note5
: registers S217 and S218 are used to synchronise transmission start:
•
either a timeout (S217)
•
or a quantity of data in the buffer memory (S218)
The first of these two limits reached triggers transmission start.
When the number of octets in the buffer memory reaches the threshold of register S218 before the timeout of register S217, it is triggering on
data.
On the other hand, when the timeout of register S217 expires before the data in the buffer memory reach the threshold of register S218, it is
triggering on time.
TX RF via S218
S217 = 10 milliseconds
S218 = 3 bytes
Condition : 3 bytes filled = transmission starts
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17
Milliseconds
TX RF via S217
S217 = 10 milliseconds
S218 = 3 bytes
Condition : 10 milliseconds without
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17
new byte = transmission starts
Milliseconds
TX RF via S218
S217 = 10 milliseconds
S218 = 3 bytes
Condition : 3 bytes received (third byte received within
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17
the 10 milliseconds time-out) = transmission starts
Milliseconds