LPC47M172 SMSC Corporation, LPC47M172 Datasheet - Page 82

• Manufacturer Part Number: LPC47M172
• Description: ADVANCED I/O CONTROLLER WITH MOTHERBOARD GLUE LOGIC
• Manufacturer: SMSC Corporation

Advanced I/O Controller with Motherboard GLUE Logic
Datasheet
Bit 3
Bit 4
Note:
Bit 5
Bit 6
Bit 7
6.28.10 Modem Status Register (MSR)
SMSC/Non-SMSC Register Sets (Rev. 02-27-04)
associated with the particular character in the FIFO it applies to.
associated character is at the top of the FIFO.
Framing Error (FE). Bit 3 indicates that the received character did not have a valid stop bit. Bit 3 is set to
a logic “1” whenever the stop bit following the last data bit or parity bit is detected as a zero bit (Spacing
level). The FE is reset to a logic “0” whenever the Line Status Register is read. 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. The Serial Port will try to resynchronize after a framing
error. To do this, it assumes that the framing error was due to the next start bit, so it samples this ‘start’ bit
twice and then takes in the ‘data’.
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 ½ bit time.
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.
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.
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.
THR and TSR are both empty,
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.
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.
DATASHEET
Page 82
In the FIFO mode this bit is set whenever the
This error is indicated when the
SMSC LPC47M172