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124
Versi on 0. 4, March/2000
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Err_RCV
R
TEMT
THRE
BI
FE
PE
OE
DR
Bits 0 RX FIFO Error
0 = RX FIFO works normally
1 = There is at least one parity error (PE), framing error (FE) or break indication (BI)
in the FIFO. LSR[0] is cleared when CPU reads the LSR and if there are no sub-
sequent errors in the RX FIFO.
Bit 1
Transmitter Empty
0 = Either Transmitter Holding Register (
THR
- TX FIFO) or Transmitter Shift Register
(
TSR
) are not empty.
1 = Both THR and TSR are empty.
Bit 2
Transmitter Holding Register Empty
0 = THR is not empty.
1 = THR is empty.
The THRE bit is set when the last data word of TX FIFO is transferred to TSR. This bit is reset
concurrently with the loading of the THR (or TX FIFO) by the CPU. This bit also causes the
UART to issue an interrupt (Irpt_THRE) to the CPU when IER[6]=1.
Bit 3
Break Interrupt indicator
This bit is set to a logic 1 whenever the received data input is held in the "spacing state"
(logic 0) for longer than a full word transmission time (that is, the total time of "start bit"
+ data bits + parity + stop bits).
Bit 4
Framing Error indicator
This bit is set to a logic 1 whenever the received character did not have a valid "stop bit"
(that is, the stop bit following the last data bit or parity bit is detected as a logic 0).
Bit 5
Parity Error indicator
This bit is set to a logic 1 whenever the received character did not have a valid "parity bit".
Bit 6
Overrun Error indicator
An overrun error will occur only after the RX FIFO is full and the next character has been
completely received in the shift register. The ccharacter in the shift register is overwritten,
but it is not transferred to the RX FIFO. OE is indicated to the CPU as soon as it happens
and is reset whenever the CPU reads the contents of the LSR.