SB16C1058_Data Sheet_EN

SB16C1058
OCTAL UART WITH 256-BYTE FIFO
JULY 2013 REV 1.04
44
7.15 Receive FIFO Count Register (RCR, Page 2)
RCR shows the number of characters that is stored in RX FIFO. In 64-byte FIFO mode, it
consists of only RCR[6:0]. If the number of characters that is stored in RX FiFO is 0, it is
shown as ‘0000_0000’ and if 64, it is shown as ‘0100_0000’. In 256-byte FIFO mode, it
consists of ISR[6] + RCR[7:0]. If the number of characters that is stored in RX FiFO is 0, it
is shown as ‘0_0000_0000’ and if 255, it is shown as ‘0_1111_1111’. And in case of the
maximum number 256, it is shown as ‘1_0000_0000’.
7.16 Flow Control Status Register (FSR, Page 2)
FSR show the status of operation of TX Hardware Flow Control, RX Hardware Flow
Control, TX Software Flow Control, and RX Software Flow Control.
Table 19: Flow Control Status Register Description
Bit
Symbol
Description
7:6
FSR[7:6]
Not used, always ‘00’.
5
FSR[5]
TX Hardware Flow Control Status.
0 : When FIFO or Auto-RTS flow control is disabled.
If FIFO and Auto-RTS flow control is enabled, it means
the number of data received in RX FIFO at the first time
is less than the value of FUR, or it means the number of
data in RX FIFO was more than the value of FUR and
after the CPU read them, the number of data that
remains unread is less than or equal to the value of FLR.
That is, UART reports external device that it can receive
more characters.
1 : It shows that the number of data received in RX FIFO
exceeds the value of FUR and UART reports external
device that it cannot receive more data. If RX FIFO has
space to store more data, new data are stored in RX
FIFO but after it gets full, they are lost.
For more details, refer to ‘6.2 Hardware Flow Control’.
4
FSR[4]
TX Software Flow Control Status.
0 : When FIFO or Software flow control is disabled.
If FIFO and Software flow control is enabled, it means
the number of data received in RX FIFO at the first time
is less than the value of FUR, or it means the number of
data in RX FIFO was more than the value of FUR and
after the CPU read them, the number of data that
remains unread after the CPU read the data received in
RX FIFO is less than or equal to the value of FLR. That
is, UART transmits Xon character to report external
device that it can receive more data.
1 : It shows that the number of data received in RX FIFO
exceeds the value of FUR and transmitting Xoff