
8.0 USART
(Continued)
PEN:
This bit enables/disables Parity (7- and 8-bit modes
only). Read/Write, cleared on reset.
PEN = 0
Parity disabled.
PEN = 1
Parity enabled.
PSEL1, PSEL0:
Parity select bits. Read/Write, cleared on
reset.
PSEL1 = 0, PSEL0 = 0
Odd Parity (if Parity enabled)
PSEL1 = 0, PSEL0 = 1
Even Parity (if Parity enabled)
PSEL1 = 1, PSEL0 = 0
Mark(1) (if Parity enabled)
PSEL1 = 1, PSEL0 = 1
Space(0) (if Parity enabled)
XBIT9/PSEL0:
Programs the ninth bit for transmission when
seven or eight data bits per frame, this bit in conjunction with
PSEL1 selects parity. Read/Write, cleared on reset.
CHL1, CHL0:
These bits select the character frame format.
Parity is not included and is generated/verified by hardware.
Read/Write, cleared on reset.
CHL1 = 0, CHL0 = 0
The frame contains eight data bits.
CHL1 = 0, CHL0 = 1
The frame contains seven data bits.
CHL1 = 1, CHL0 = 0
The frame contains nine data bits.
CHL1 = 1, CHL0 = 1
Loopback Mode selected. Trans-
mitter output internally looped back
to receiver input. Nine bit framing
format is used.
ERR:
This bit is a global USART error flag which gets set if
any or a combination of the errors (DOE, FE, PE) occur.
Read only; it cannot be written by software, cleared on reset.
RBFL:
This bit is set when the USART has received a
complete character and has copied it into the RBUF register.
It is automatically reset when software reads the character
from RBUF. Read only; it cannot be written by software,
cleared on reset.
TBMT:
This bit is set when the USART transfers a byte of
data from the TBUF register into the TSFT register for trans-
mission. It is automatically reset when software writes into
the TBUF register. Read only, bit is set to “one” on reset; it
cannot be written by software.
ENUR-USART Receive Control and Status Register
(Address at 0BB)
DOE
FE
PE
Reserved
(Note 16)
RBIT9
ATTN
XMTG
RCVG
Bit 7
Bit 0
Note 16:
Bit is reserved for future use. User must set to zero.
DOE:
Flags a Data Overrun Error. Read only, cleared on
read, cleared on reset.
DOE = 0
Indicates no Data Overrun Error has been de-
tected since the last time the ENUR register
was read.
DOE = 1
Indicates the occurrence of a Data Overrun
Error.
FE:
Flags a Framing Error. Read only, cleared on read,
cleared on reset.
FE = 0
Indicates no Framing Error has been detected
since the last time the ENUR register was read.
FE = 1
Indicates the occurrence of a Framing Error.
PE:
Flags a Parity Error. Read only, cleared on read, cleared
on reset.
PE = 0
Indicates no Parity Error has been detected since
the last time the ENUR register was read.
Indicates the occurrence of a Parity Error.
SPARE:
Reserved for future use. Read/Write, cleared on
reset.
RBIT9:
Contains the ninth data bit received when the US-
ART is operating with nine data bits per frame. Read only,
cleared on reset.
ATTN:
ATTENTION Mode is enabled while this bit is set.
This bit is cleared automatically on receiving a character with
data bit nine set. Read/Write, cleared on reset.
XMTG:
This bit is set to indicate that the USART is transmit-
ting. It gets reset at the end of the last frame (end of last Stop
bit). Read only, cleared on reset.
RCVG:
This bit is set high whenever a framing error occurs
and goes low when RDX goes high. Read only, cleared on
reset.
ENUI-USART Interrupt and Clock Source Register
(Address at 0BC)
PE = 1
STP2
Bit 7
STP78
ETDX
SSEL XRCLK XTCLK
ERI
ETI
Bit 0
STP2:
This bit programs the number of Stop bits to be
transmitted. Read/Write, cleared on reset.
STP2 = 0
One Stop bit transmitted.
STP2 = 1
Two Stop bits transmitted.
STP78:
This bit is set to program the last Stop bit to be 7/8th
of a bit in length. Read/Write, cleared on reset.
ETDX:
TDX (USART Transmit Pin) is the alternate function
assigned to Port L pin L2; it is selected by setting ETDX bit.
To simulate line break generation, software should reset
ETDX bit and output logic zero to TDX pin through Port L
data and configuration registers. Read/Write, cleared on
reset.
SSEL:
USART mode select. Read/Write, cleared on reset.
SSEL = 0
Asynchronous Mode.
SSEL = 1
Synchronous Mode.
XRCLK:
This bit selects the clock source for the receiver
section. Read/Write, cleared on reset.
XRCLK = 0
The clock source is selected through the
PSR and BAUD registers.
XRCLK = 1
Signal on CKX (L1) pin is used as the clock.
XTCLK:
This bit selects the clock source for the transmitter
section. Read/Write, cleared on reset.
XTCLK = 0
The clock source is selected through the PSR
and BAUD registers.
XTCLK = 1
Signal on CKX (L1) pin is used as the clock.
ERI:
This bit enables/disables interrupt from the receiver
section. Read/Write, cleared on reset.
ERI = 0
Interrupt from the receiver is disabled.
ERI = 1
Interrupt from the receiver is enabled.
ETI:
This bit enables/disables interrupt from the transmitter
section. Read/Write, cleared on reset.
ETI = 0
Interrupt from the transmitter is disabled.
ETI = 1
Interrupt from the transmitter is enabled.
C
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