New option for the STXD instruction to send several characters without delay.

FAQ #100916

The character mode supports now a new option to delay the sending of character at any time (also called "Freeze Mode"). This allows filling up an intermediary sending buffer without that the characters are really transmitted over the serial line until the transmission is enabled.



This new mode (freeze mode) has been implemented in order to avoid pauses within the transmission of a block of characters (especially for time-critical protocol such as Modbus). Instead of sending a character right after it has been written to the buffer with the STXD instruction, the new STXD_Enable flag allows the user to send the character block by block.

To use this option a new parameter (STXD_Enable flag) has to be insert in the SASI Text as showing below:
 TEXT 1 "UART:115200,8,N,1;MODE:MC0,F0;DIAG:F10,R10;TBUF:512"

Description of the STXD_Enable flag

  • If the STXD_Enable flag (sometimes called "freeze bit") is set to 1:
    Any STXD instruction will insert the character in the sending buffer whiteout that the characters are really transmitted over the serial line.
  • If the STXD_Enable flag is set to 0:
    The next STXD instruction will transmit the content of the sending buffer in one go with all character that have been entered before.

Before the STXD_Enable flag is set to 1 (stop sending), the user has to take care about TBSY flag. In case the PCD has not finish sending its last block, the communication will be blocked, for this reason the STXD is refused with NEXE flag is set.

Supported PCD Systems and minimum FW which does support the new STXD_Enable flag:  PCD System Minimum FW

 PCD System  first production firmware supporting the "Freeze Mode" 


  • The STXD_Enable flag has no effect for STXT instruction.
  • If the Sasi text does not contains the STXD_Enable flag then the character which is transmitted with the STXD instruction will be transmitted immediately after the execution of the STXD instruction.
  • The size of the intermediary sending buffer is the same as defined with the “TBUF:” parameter on the SASI text.


PG5 2.0 / Mode-C

Last update: 24.05.2015 16:51

First release: 31.03.2008 13:29

Views: 23581

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