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

12. Asynchronous Serial interface (UART1 )
12.9 Status Flag
UART1SR<RBFL>
RXD1 pin
Shift register
RD1BUF
UART1SR<OERR>
INTRXD1 interrupt
Note:Receive operations are disabled until the overrun error flag UART1SR<OERR> is cleared.

12.9.4 Receive Data Buffer Full

Loading the received data in RD1BUF sets receive data buffer full flag UART1SR<RBFL> to "1". The
UART1SR<RBFL> is cleared to "0" when the RD1BUF is read after reading the UART1SR.
RXD1 pin
Shift register
RD1BUF
UART1SR<RBFL>
INTRXD1 interrupt
Note:If the overrun error flag UART1SR<OERR> is set during the period between reading the UART1SR and read-

12.9.5 Transmit Data Buffer Empty

When no data is in the transmit buffer TD1BUF, that is, when data in TD1BUF are transferred to the transmit
shift register and data transmit starts, transmit data buffer empty flag UART1SR<TBEP> is set to "1". The
UART1SR<TBEP> is cleared to "0" when the TD1BUF is written after reading the UART1SR.
xxx0 **
yyyy
Figure 12-7 Generation of Overrun Error
xxx0 **
yyyy
Figure 12-8 Generation of Receive Data Buffer Full
ing the RD1BUF, it cannot be cleared by only reading the RD1BUF. Therefore, after reading the RD1BUF,
read the UART1SR 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
*
Page 146
T5CL8
1xxxx0
After reading UART1SR then
RD1BUF clears OERR.
1xxxx0
xxxx
After reading UART1SR then
RD1BUF clears RBFL.