UT1750AR12WCC Просмотр технического описания (PDF) - Aeroflex UTMC

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UT1750AR12WCC

RISC Microprocessor

Aeroflex UTMC 

UART Receiver Register (RCVR)

The UART Receiver Buffer Register (see figure 9) receives

9600-baud asynchronous serial data through the UARTIN input

pin on the UT1750AR. Each serial data string contains an active-

low Start bit, eight Data bits, an odd Parity bit, and an active-

high Stop bit. Figure 10 shows a single serial data string.

15 14 13 12 11 10 9

0 000000

876 54 3210

RR RRRRRR

CC CCCCCC

DD DDDDDD

076 543210

MSB

LSB

Figure 9. The UART Receiver

UART Transmitter Buffer Register (TXMT)

The UT1750AR’s internal UART forms an 11-bit serial data

string by combining a Start bit, the eight Data bits from the

Transmitter Buffer Register (TXMT), an odd Parity bit, and a

Stop bit. Figure 11 shows the composition of the serial data

string.

The UT1750AR transmits this serial data string through the

UARTOUT pin at a rate of 9600 baud.

DIRECTION

OF DATA

FLOW OUT

OF THE

UT1750AR

S T TTT TTTT

T X X XX X X XX

R D D D D DD D D

T 0 123 45 67

S

PT

AO

RP

Figure 11. UART Transmitter Data String

DATA

FLOW

S R RRR RRRR

S

T C C CC C C CC P T

R D D D D DD D D AO

T 0 1 2 3 4 5 6 7 RP

Figure 10. UART Receiver Data String

While receiving a serial data string, the UT1750AR generates

four status flags: Data Ready (DR); Overrun Error (OE);

Framing Error (FE); and Parity Error (PE). The UT1750AR

stores these status bits in the System Status Register (STATUS).

Receiver buffer register bits 15-8 are always low. Bit numbers

7-0 (RCD7-RCD0) contain data the UT1750AR receives via the

serial data port. RCD7 is the MSB; RCD0 is the LSB.

Two status signals are associated with transmitting serial data.

These signals are the UART Transmitter Buffer Empty (TBE)

and UART Transmitter Register Empty (TE). TBE and TE are

both active high and provide information on the status of double

buffering the UART’s transmitted data. TBE and TE are read

from the System Status Register as bits 2 and 1, respectively.

The UT1750AR’s internal UART has a double-buffered data

transmission scheme (figure 12). The UT1750AR first loads the

data for transmission into the Transmitter Buffer Register. If the

UART Transmitter Register is empty, data from the TXMT

automatically transfers to the UART Transmitter Register. At

this time, the TBE bit goes active indicating more data may be

loaded into the TXMT. This double-buffering scheme allows

contiguous transmission of serial data streams and also

decreases the UT1750AR’s required overhead for the UART

interface.

THE UT1750AR’S INTERNAL

DATA BUS

UART TRANSMITTER BUFFER

REGISTER (TBR)

16

STATUS OF THE

D

C

D

C

D

C

D

C

D

C

D

C

D

C

D

C

T

X

D

T

X

D

T

X

D

T

X

D

T

X

D

T

X

D

T

X

D

T

X

D

TBR IS READ

FROM BIT 2

OF THE SYSTEM

7 6 5 4 3 2 1 0 STATUS REGISTER

DATA IS LOADED INTO THE

TBR WITH AN OUTPUT

REGISTER (OTR) INSTRUCTION

STATUS OF THE UART

TRANSMITTER REGISTER IS

READ FROM BIT 1

OF THE SYSTEM STATUS

REGISTER

UART TRANSMITTER

REGISTER

8

SPT T T T T T T T S

T AXXXXXXXXT

OR7 6 5 4 3 2 1 0 R

P

T

DIRECTION OF

DATA FLOW

Figure 12. The UT1750AR UART Double-Buffered Transmitter Register

16

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