Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 126)

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126 Rev. 1.3
Prior to sending the ATDT to establish a synchronous access mode connection, the following commands and
registers require initialization: +MS, +ES, +ESA, +ITF, +IFC, U87, and U7A.
As an example, the closest equivalent to the Legacy Synchronous DCE Mode is the following initialization setting.
With either Synchronous Access Submode, once a connection has been established, payload data are multiplexed
with command/indicator information by use of shielding. With shielding, either of the two bytes
<0x19> or <0x99> (used to represent ) precedes a special command or special indicator.
Synchronous access mode shielding is designed to support XON/XOFF handshaking. As such, the bytes
0x13 and 0x11 (XON/XOFF) are considered to be special characters in the same way the 0x19 and 0x99 bytes,
used for , are special.
Since the payload data are multiplexed with shielded command/indicator and possibly XON/XOFF
characters, Transparency codes are defined for the purpose of allowing the host software to send 0x13,
0x11, 0x19 and 0x99 bytes to/from the DCE. For example, if one <0x99> character needs to be sent as payload,
the host software sends <0x76> instead. For a complete list commands and statuses, see Table 86.
Table 85. Synchronous Access Mode Settings
AT\N0
Required to disable MNP,V.42
and other protocols
AT+ES = 6,,8
Enable synchronous access
mode on originate or answer
AT+ESA = 0,0,0,,1,0
Send Abort on underrun/over-
run in Framed Submode.
Enable CRC generation and
checking.
AT+IFC = 2,2 CTS/RTS Flow Control
AT+ITF = 0383,0128
Controls CTS Flow Control
Threshold. CTS off at 383
bytes, CTS On at 128 bytes.
AT:U87,050A
Direct to Framed Sub-mode
upon connection. DCE starts
to transmit upon receipt of 10
bytes from the DTE.