UT82CRH51AC-36WPC Ver la hoja de datos (PDF) - Aeroflex UTMC

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UT82CRH51AC-36WPC

UT82CRH51A USART

Aeroflex UTMC 

D(7:0)

RESET

CLK

C/D

RD

WR

CS

DSR

DTR

CTS

RTS

DATA

BUS

BUFFER

READ/WRITE

CONTROL

LOGIC

MODEM

CONTROL

TRANSMIT

BUFFER

(P-S)

TRANS-

MITTER

CONTROL

RECEIVE

BUFFER

(S-P)

RECEIVER

CONTROL

TxD

TxRDY

TxEMPTY

TxC

RxD

RxRDY

RxC

SYNDET/

BRKDET

Figure 4. UT82CRH51A Block Diagram Showing Data Bus Buffer

and Read/Write Logic Functions

1.2.4 RD (Read)

A "low" on this input informs the UT82CRH51A the CPU is

reading data or status information from the UT82CRH51A (fig-

ure 4).

C/D RD WR CS

0

0

1

0

DATA -> DATA BUS

0

1

0

0

DATA BUS -> DATA

1

0

1

0

STATUS -> DATA BUS

1

1

0

0

DATA BUS -> CONTROL

X

1

1

0

DATA BUS -> 3-STATE

X

X

X

1

DATA BUS -> 3-STATE

1.2.5 C/D (Control/Data)

This input, in conjunction with the WR and RD inputs, informs

the UT82CRH51A the word on the Data Bus is either a data

character, control word or status information.

1 = CONTROL/STATUS; 0 = DATA

1.2.6 CS (Chip Select)

A "low" on this input selects the UT82CRH51A. No reading or

writing will occur unless the device is selected. When CS is

high, the Data Bus is in the float state and RD and WR have no

effect on the chip.

1.3 MODEM CONTROL

The UT82CRH51A has a set of control inputs and outputs that

can be used to simplify the interface to almost any modem. The

modem control signals are general purpose in nature and can be

used to functions, other than modem control, if necessary (figure

5).

1.3.1 DSR (Data Set Ready)

The DSR input signal is a general-purpose, 1-bit inverting input

port. Its condition can be tested by the CPU using a Status Read

operation. The DSR input is normally used to test modem con-

ditions such as Data Set Ready.

1.3.2 DTR (Data Terminal Ready)

The DTR output signal is a general-purpose, 1-bit inverting out-

put port. It can be set "low" by programming the appropriate bit

in the Command Instruction word. The DTR output signal is

normally used for modem control such as Data Terminal Ready.

1.3.3 RTS (Request to Send)

The RTS output signal is a general-purpose, 1-bit inverting out-

put port. It can be set "low" by programming the appropriate bit

in the Command Instruction word. The RTS output signal is

normally used for modem control such as Request to Send.

1.3.4 CTS (Clear to Send)

A "low" on this input enables the UT82CRH51A to transmit se-

rial data if the TxEnable bit in the Command byte is set to a

"one". If either a TxEnable off or CTS off condition occurs

while the Tx is in operation, the Tx transmits all the data in the

USART written prior to TxDisable command before shutting

down.

1.4 TRANSMIT BUFFER

The Transmit Buffer Accepts parallel data from the Data Bus

Buffer, converts it to a serial bit stream, inserts the appropriate

characters or bits (based on the communication technique) and

outputs a composite serial stream of data on the TxD output pin

on the falling edge of TxC. The transmitter begins transmission

upon being enabled if CTS = 0. The TxD line will be held in the

marking state immediately upon a master Reset or when TxEn-

able or CTS is off or the transmitter is empty (figure 5).

1.5.TRANSMITTER CONTROL

The Transmitter Control manages all activities associated with

the transmission of serial data. It accepts and issues signals both

externally and internally to accomplish this function (figure 5).

1.5.1 TxRDY (Transmitter Ready)

This output signals the CPU the transmitter is ready to accept a

data character. The TxRDY output pin can be used as an inter-

rupt to the system since it is masked by TxEnable; or, for Polled

operation, the CPU can check TxRDY using a Status Read op-

eration. TxRDY is automatically reset by the leading edge of

WR when a data character is loaded from the CPU.

Note: When using the Polled operation, the TxRDY status bit

is not masked by TxEnable, but will only indicate the Empty/

Full Status of the Tx Data Input Register.

1.5.2 TxEMPTY (Transmitter Empty)

When the UT82CRH51A has no characters to send, the TxEMP-

TY output will go "high". It resets upon receiving a character

3

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