Receive Data Buffer Full; Transmit Data Buffer Empty - Philips CEM2100/00 Service Manual

13. Asynchronous Serial interface (UART2 )
13.9 Status Flag
UART2SR<RBFL>
RXD2 pin
Shift register
RD2BUF
UART2SR<OERR>
INTRXD2 interrupt
Note:Receive operations are disabled until the overrun error flag UART2SR<OERR> is cleared.

13.9.4 Receive Data Buffer Full

Loading the received data in RD2BUF sets receive data buffer full flag UART2SR<RBFL> to "1". The
UART2SR<RBFL> is cleared to "0" when the RD2BUF is read after reading the UART2SR.
RXD2 pin
Shift register
RD2BUF
UART2SR<RBFL>
INTRXD2 interrupt
Note:If the overrun error flag UART2SR<OERR> is set during the period between reading the UART2SR and read-

13.9.5 Transmit Data Buffer Empty

When no data is in the transmit buffer TD2BUF, that is, when data in TD2BUF are transferred to the transmit
shift register and data transmit starts, transmit data buffer empty flag UART2SR<TBEP> is set to "1". The
UART2SR<TBEP> is cleared to "0" when the TD2BUF is written after reading the UART2SR.
xxx0 **
yyyy
Figure 13-7 Generation of Overrun Error
xxx0 **
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Figure 13-8 Generation of Receive Data Buffer Full
ing the RD2BUF, it cannot be cleared by only reading the RD2BUF. Therefore, after reading the RD2BUF,
read the UART2SR again to check whether or not the overrun error flag which should have been cleared still
remains set.
Stop
Final bit
xxxx0
*
Final bit Stop
xxxx0
*
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T5CL8
1xxxx0
After reading UART2SR then
RD2BUF clears OERR.
1xxxx0
xxxx
After reading UART2SR then
RD2BUF clears RBFL.