CIRCC datasheet(44/70 Pages) SMSC

44 / 70 page

Bit 0

This bit controls the Data Terminal Ready (nDTR)

output. When bit 0 is set to a logic "1", the nDTR

output is forced to a logic "0". When bit 0 is a

logic "0", the nDTR output is forced to a logic "1".

Bit 1

This bit controls the Request To Send (nRTS)

output. Bit 1 affects the nRTS output in a manner

identical to that described above for bit 0.

Bit 2

This bit controls the Output 1 (OUT1) bit. This bit

does not have an output pin and can only be read

or written by the CPU.

Bit 3

Output 2 (OUT2). This bit is used to enable an

UART interrupt. When OUT2 is a logic "0", the

serial port interrupt output is forced to a high

impedance state - disabled.

When OUT2 is a

logic "1", the serial port interrupt outputs are

enabled.

Bit 4

This

bit

provides

the

loopback

feature

for

diagnostic testing of the Serial Port. When bit 4 is

set to logic "1", the following occur:

1. The TXD is set to the Marking State(logic "1").

2. The

receiver

Serial

Input

(RXD)

disconnected.

3. The output of the Transmitter Shift Register is

"looped back" into the Receiver Shift Register

input.

4. All MODEM Control inputs (nCTS, nDSR, nRI

and nDCD) are disconnected.

5. The four MODEM Control outputs (nDTR,

nRTS, and OUT2) are internally connected to

the four MODEM Control inputs.

6. The Modem Control output pins are forced

inactive high.

7. Data

that

transmitted

immediately

received.

This feature allows the processor to verify the

transmit and receive data paths of the Serial Port.

In the diagnostic mode, the receiver and the

transmitter interrupts are fully operational. The

MODEM Control Interrupts are also operational

but the interrupts' sources are now the lower four

bits of the MODEM Control Register instead of the

MODEM Control inputs. The interrupts are still

controlled by the Interrupt Enable Register.

Bits 5 through 7

These bits are permanently set to logic zero.

LINE STATUS REGISTER (LSR)

Address Offset = 5H, DLAB = X, READ/

WRITE

Bit 0

Data Ready (DR). It is set to a logic "1" whenever

a complete incoming character has been received

and transferred into the Receiver Buffer Register

or the FIFO. Bit 0 is reset to a logic "0" by reading

all of the data in the Receive Buffer Register or the

FIFO.

Bit 1

Overrun Error (OE). Bit 1 indicates that data in the

Receiver Buffer Register was not read before the

next character was transferred into the register,

thereby destroying the previous character.

FIFO mode, an overrun error will occur only when

the FIFO is full and the next character has been

completely received in the shift register, the

character in the shift register is overwritten but not

transferred to the FIFO. The OE indicator is set to

a logic "1" immediately upon detection of an

overrun condition, and reset whenever the Line

Status Register is read.

Bit 2

Parity Error (PE). Bit 2 indicates that the received

data character does not have the correct even or

odd parity, as selected by the even parity select

bit. The PE is set to a logic "1" upon detection of a

parity error and 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.

CIRCC датащи(PDF) 44 Page - SMSC Corporation

CIRCC датащи(HTML) 44 Page - SMSC Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

датащи скачать

ссылки URL