UT82CRH51AC-36WCX データシートの表示（PDF） - Aeroflex UTMC

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UT82CRH51AC-36WCX

UT82CRH51A USART

Aeroflex UTMC 

4.0 STATUS READ DEFINITION

In data communication systems it is often necessary to examine

the "status" of the active device to ascertain if errors have oc-

curred or other conditions requiring the processor’s attention.

The UT82CRH51A has facilities that allow the programmer to

"read" the status of the device at any time during the functional

operation. (Status update is inhibited during status read.)

A normal "read" command is issued by the CPU with C/D = 1 to

accomplish this function.

Some of the bits in the Status Read Format have identical mean-

ings to external output pins to that the UT82CRH51A can be

used in a completely polled or interrupt-driven environment.

TxRDY is an exception (figure 15).

Note: Status update can have a maximum delay of 28 clock pe-

riods from the actual event affecting the status.

D7

D6

D5

D4

D3

D2

D1

D0

DSR SYN- FE OE

DET/

PE Tx- RxR TxRD

EMP- DY Y

Note 1

SAME DEFINITION AS I/O PINS

PARITY ERROR

The PE flag is set when a parity error

is detected. It is reset by the ER bit of

the Command Instruction. PE does

not inhibit operation of the

UT82CRH51A

OVERRUN ERROR

The OE flag is set when the CPU

does not read a character before the

next one becomes available. It is re-

set by the ER bit of the Command

Instruction. OE does not inhibit op-

eration of the UT82CRH51A how-

ever, the previously overrun

character is lost.

FRAMING ERROR (Async only)

The FE flag is set when a valid Stop

bit is not detected at the end of every

character. It is reset by the ER bit of

the Command Instruction. FE does

not inhibit the operation of the

UT82CRH51A

DATA SET READY

Indicates that the DSR is at a zero

level.

Note : TxRDY status bit has different meanings from the TxRDY output pin.

The former is not conditioned by CTS and TxEN; the latter is conditioned by

both CTS and TxEN.

i.e TxRDY status bit = DB Buffer Empty

TxRDY pin out = DB Buffer Empty + (CTS-0) + (TxEN-1)

Figure 15. Status Read Format

10

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