Quatech DS-202 User Manual - page 15
FUNCTIONAL DESCRIPTION
B i t s B I , F E , P E , a n d O E a r e t h e s o u r c e s o f
r e c e i v e r l i n e s t a t u s i n t e r r u p t s . T h e s e b i t s
a r e r e s e t b y r e a d i n g t h e l i n e s t a t u s r e g i s t e r .
In FIFO mode* , these bits are associated with a
s p e c i f i c c h a r a c t e r i n t h e F I F O a n d t h e
e x c e p t i o n i s r e v e a l e d o n l y w h e n t h a t c h a r a c t e r
reaches the top of the FIFO.
BI - Break Interrupt:
Indicates the receive data input has been in the
spacing state (logic 0) for longer than one full
word transmission time.
FIFO mode: *
O n l y o n e z e r o c h a r a c t e r i s l o a d e d i n t o t h e F I F O
and transfers are disabled until SIN goes to the
m a r k s t a t e ( l o g i c 1 ) a n d a v a l i d s t a r t b i t i s
received.
FE - Framing Error:
I n d i c a t e s t h e r e c e i v e d c h a r a c t e r h a d a n i n v a l i d
s t o p b i t . T h e s t o p b i t f o l l o w i n g t h e l a s t d a t a
or parity bit was a 0 bit (spacing level).
PE - Parity Error:
I n d i c a t e s t h a t t h e r e c e i v e d d a t a d o e s n o t h a v e
the correct parity.
OE - Overrun Error:
Indicates the receive buffer was not read before
t h e n e x t c h a r a c t e r w a s r e c e i v e d a n d t h e
character is destroyed.
FIFO mode: *
Indicates the FIFO is full and another character
has been shifted in. The character in the shift
r e g i s t e r i s d e s t r o y e d b u t i s n o t t r a n s f e r r e d t o
the FIFO.
DR - Data ready:
I n d i c a t e s d a t a i s p r e s e n t i n t h e r e c e i v e b u f f e r
o r F I F O . D R i s r e s e t b y r e a d i n g t h e r e c e i v e
buffer register or receiver FIFO.
* with optional 16550.