2.8.6.3 Start of Telegram (SOT)

A WCO indicates that a valid RF signal is present. Now, the precise start of the data payload must be determined. This event is called the start of telegram (SOT). The SOT is usually determined by a well-defined start frame ID (SFID) pattern. The following SOT check conditions can be enabled independently for path A and path B of each service in the eepServices.SOT2x variables:

  • Manchester coding check (MANOEx)
  • Symbol timing check (SYTOEx)
  • Modulation amplitude check (AMPOEx)
  • Carrier check (CAROEx)
  • RSSI range check (RROEx)
  • Wake-up pattern check (WUPEx)
  • Start frame ID pattern check (SFIDEx)
  • Wake check OK from other path (WCOxOE)

Address Service0

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0x00F3

SOT2A

WCOBOE

RROEA

SFIDEA

WUPEA

MANOEA

SYTOEA

AMPOEA

CAROEA

0x00F4

SOT2B

WCOAOE

RROEB

SFIDEB

WUPEB

MANOEB

SYTOEB

AMPOEB

CAROEB

By default, the Manchester, symbol timing, modulation amplitude, carrier (FSK only) and SFID pattern checks are activated as SOT condition.

The functionality and configuration of the checks is described in detail in Telegram Settings and Signal Checks.

If any of the following checks is enabled as SOT check in the SOT2x variable, the corresponding EOT2x check (compare End of Telegram (EOT)) must be activated: Manchester coding, symbol timing, modulation amplitude, carrier check or RSSI range check.

Address Service0

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0x00C8

EOT2A

EOTBFE

RRFEA

TELREA

TMOFEA

MANFEA

SYTFEA

AMPFEA

CARFEA

0x00C9

EOT2B

EOTAFE

RRFEB

TELREB

TMOFEB

MANFEB

SYTFEB

AMPFEB

CARFEB

An SOT is triggered as soon as all enabled checks pass. A check that already passed for WCO is stored as successful and does not have to pass again for SOT unless there is a path restart between WCO and SOT. This is relevant if the gap mode is enabled (compare Figure 2-24 for the occurrence of path restarts).

Consequently, in standard applications, the SFID pattern check is the only check that has to pass between WCO and SOT as all other checks were already successful for WCO.