FUNCTIONAL

DESCRIPTION

 

 

F . LINE

STATUS

REGISTER

 

 

+------

+

 

 

 

 

 

D7

FFRX

-----

Error

in FIFO RCVR

(FIFO only)

 

+------

+

 

 

 

 

 

D6

TEMT

-----

Transmitter

empty

 

 

+------

+

 

 

 

 

 

D5

THRE

-----

Transmitter

holding

register empty

 

+------

+

 

 

 

 

 

D4

BI

-----

Break

interrupt

 

 

+------

+

 

 

 

 

 

D3

FE

-----

Framing

error

 

 

+------

+

 

 

 

 

 

D2

PE

-----

Parity

error

 

 

 

+------

+

 

 

 

 

 

D1

OE

-----

Overrun

error

 

 

+------

+

 

 

 

 

 

D0

DR

-----

Data ready

 

 

 

+------

+

 

 

 

 

 

Figure 12. Line status register bit definitions.

FFRX -

FIFO Receiver Error:

 

 

Always logic 0 in character mode.

FIFO

mode:

 

 

 

 

I n d i c a t e s o n e o r m o r e p a r i t y e r r o r s , f r a m i n g

 

 

e r r o r s , o r b r e a k i n d i c a t i o n s i n t h e r e c e i v e r

 

 

FIFO. FFRX is reset by reading the line status

 

 

register.

 

TEMT

-

Transmitter

Empty:

 

 

Indicates

the transmitter holding register (or

 

 

F I F O ) a n d t h e t r a n s m i t t e r s h i f t r e g i s t e r a r e

 

 

empty and are ready to receive new data. TEMT is

 

 

reset by writing a character to the transmitter

 

 

holding

register.

THRE -

Transmitter Holding Register Empty:

 

 

Indicates

the transmitter holding register (or

 

 

F I F O ) i s e m p t y a n d i t i s r e a d y t o a c c e p t n e w

 

 

d a t a .

T H R E i s r e s e t b y w r i t i n g d a t a t o t h e

 

 

transmitter

holding register (or FIFO).

iii

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Image 14
IBM DS-2000 warranty Functional Description Line Status Register, Ffrx, Temt, Thre