LPC47N227TQFP Standard Microsystems (SMSC), LPC47N227TQFP Datasheet - Page 76

• Manufacturer Part Number: LPC47N227TQFP
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LPC47N227TQFP

• Lead Free Status / RoHS Status: Not Compliant

Bit 4
Break Interrupt (BI). Bit 4 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 the start bit + data bits +
parity bits + stop bits). The BI is reset after the CPU reads the contents of the Line Status Register. In the
FIFO mode this error is associated with the particular character in the FIFO it applies to. This error is
indicated when the associated character is at the top of the FIFO. When break occurs only one zero
character is loaded into the FIFO. Restarting after a break is received, requires the serial data (RXD) to
be logic "1" for at least 1/2 bit time.
Note: Bits 1 through 4 are the error conditions that produce a Receiver Line Status Interrupt whenever
any of the corresponding conditions are detected and the interrupt is enabled.
Bit 5
Transmitter Holding Register Empty (THRE). Bit 5 indicates that the Serial Port is ready to accept a new
character for transmission. In addition, this bit causes the Serial Port to issue an interrupt when the
Transmitter Holding Register interrupt enable is set high. The THRE bit is set to a logic "1" when a
character is transferred from the Transmitter Holding Register into the Transmitter Shift Register. The bit is
reset to logic "0" whenever the CPU loads the Transmitter Holding Register. In the FIFO mode this bit is
set when the XMIT FIFO is empty, it is cleared when at least 1 byte is written to the XMIT FIFO. Bit 5 is a
read only bit.
Bit 6
Transmitter Empty (TEMT). Bit 6 is set to a logic "1" whenever the Transmitter Holding Register (THR)
and Transmitter Shift Register (TSR) are both empty. It is reset to logic "0" whenever either the THR or
TSR contains a data character. Bit 6 is a read only bit.
In the FIFO mode this bit is set whenever the
THR and TSR are both empty.
Bit 7
This bit is permanently set to logic "0" in the 450 mode. In the FIFO mode, this bit is set to a logic "1"
when there is at least one parity error, framing error or break indication in the FIFO. This bit is cleared
when the LSR is read if there are no subsequent errors in the FIFO.
Modem Status Register (MSR)
Address Offset = 6H, DLAB = X, READ/WRITE
This 8 bit register provides the current state of the control lines from the MODEM (or peripheral device). In
addition to this current state information, four bits of the MODEM Status Register (MSR) provide change
information. These bits are set to logic "1" whenever a control input from the MODEM changes state.
They are reset to logic "0" whenever the MODEM Status Register is read.
Bit 0
Delta Clear To Send (DCTS). Bit 0 indicates that the nCTS input to the chip has changed state since the
last time the MSR was read.
Bit 1
Delta Data Set Ready (DDSR). Bit 1 indicates that the nDSR input has changed state since the last time
the MSR was read.
Bit 2
Trailing Edge of Ring Indicator (TERI). Bit 2 indicates that the nRI input has changed from logic "0" to
logic "1".
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