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Restriction on Use of the SIO Error Flag in UART Mode

Product name
TOSHIBA Microcontrollers TX19 Family TX19 Series
  • TMP1942CYU
  • TMP1942CZU
  • TMP1942FDU
  • TMP1942CZXB
  • TMP1942FDXB

Dear Customer

With regard to the TX19 Family microcontrollers listed above, Toshiba have found a restriction on use of the SIO error flag in UART mode. Under the condition described below, the error flag may not be read correctly.

In SIO receive operations in UART mode, if the framing error flag that has been set is read simultaneously with completion of a receive operation, the flag may be cleared to “0” without the error state (“1”) being detected. (The framing error flag is automatically cleared to “0” when it is read.)
Counter Measure
Please avoid the above problem by programming as described below.
For detecting a framing error, do not poll the framing error flag (the FERR bit in the SCxCR register). Instead, read the framing error flag in the interrupt service routine before reading the receive buffer.
For details, refer to the programming example in “3.11.4 (3) Mode 2 (8-bit UART mode)” in the technical datasheet.
Example of interrupt routine processing
INTCLR ← XX110000 Clears the interrupt request.
Reg. ← SC0CR AND 0x1C Checks for errors.
if Reg. ≠ 0 then ERROR
Reg. ← SC0BUF Reads received data
End of interrupt processing
X: Don’t care  -: No change


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