sc28l198 NXP Semiconductors, sc28l198 Datasheet - Page 24

• Manufacturer Part Number: sc28l198
• Description: Octal Uart For 3.3v And 5v Supply Voltage
• Manufacturer: NXP Semiconductors

Philips Semiconductors
SR[5] – Parity Error (PE)
This bit is set when the ’with parity’ or ’force parity’ mode is
programmed and the corresponding character in the FIFO was
received with incorrect parity. In the special ’wake up mode’, the
parity error bit stores the received A/D bit.
SR[4] – Overrun Error (OE)
This bit, when set, indicates that one or more characters in the
received data stream have been lost. It is set upon receipt of a new
character when the RxFIFO is full and a character is already in the
receive shift register waiting for an empty FIFO position. When this
occurs, the character in the receive shift register (and its break
detect, parity error and framing error status, if any) is lost. This bit is
cleared by a reset error status command.
SR[3] – Transmitter Empty (TxEMT)
This bit is set when the transmitter underruns, i.e., both the TxFIFO
and the transmit shift register are empty.
It is set after transmission of the last stop bit of a character, if no
character is in the TxFIFO awaiting transmission. It is reset when
the TxFIFO is loaded by the CPU, or when the transmitter is
disabled.
Table 11. ISR – Interrupt Status Register
This register provides the status of all potential interrupt sources for
a UART channel. When generating an interrupt arbitration value,
the contents of this register are masked by the interrupt mask
register (IMR). If a bit in the ISR is a ’1’ and the corresponding bit in
the IMR is also a ’1’, interrupt arbitration for this source will begin. If
the corresponding bit in the IMR is a zero, the state of the bit in the
ISR can have no affect on the IRQN output. Note that the IMR may
or may not mask the reading of the ISR as determined by MR1[6].
If MR1[6] is cleared, the reset and power on default, the ISR is read
without modification. If MR1[6] is set, the a read of the ISR gives a
value of the ISR ANDed with the IMR.
ISR[7] – Input Change of State
This bit is set when a change of state occurs at the I/O1 or I/O0
input pins. It is reset when the CPU reads the Input Port Register,
IPR.
ISR[6] Watch-dog Time–out
This bit is set when the receiver’s watch-dog timer has counted
more than 64 bit times since the last RxFIFO event. RxFIFO events
are a read of the RxFIFO or GRxFIFO, or the push of a received
character into the FIFO. The interrupt will be cleared automatically
upon the push of the next character received or when the RxFIFO or
GRxFIFO is read. The receiver watch-dog timer is included to allow
detection of the very last characters of a received message that may
be waiting in the RxFIFO, but are too few in number to successfully
initiate an interrupt. Refer to the watch-dog timer description for
details of how the interrupt system works after a watch-dog
time–out.
ISR[5] – Address Recognition Status Change
This bit is set when a change in receiver state has occurred due to
an Address character being received from an external source and
2006 Aug 10
Bit 7
I/O Port
change of
state
Octal UART for 3.3 V and 5 V supply voltage
Bit 6
Receiver
Watch-dog
Time–out
Bit 5
Address recogni-
tion event
Bit 4
Xon/off
event
Bit 3
Always 0
24
Bit 2
Change of
Break State
SR[2] – Transmitter Ready (TxRDY)
This bit, when set, indicates that the TxFIFO is ready to be loaded
with a character. This bit is cleared when the TxFIFO is loaded by
the CPU and is set when the last character is transferred to the
transmit shift register. TxRDY is reset when the transmitter is
disabled and is set when the transmitter is first enabled, e.g.,
characters loaded in the TxFIFO while the transmitter is disabled will
not be transmitted.
SR[1] – RxFIFO Full (RxFULL)
This bit is set when a character is transferred from the receive shift
register to the receive FIFO and the transfer causes the FIFO to
become full, i.e., all sixteen RxFIFO positions are occupied. It is
reset when the CPU reads the RxFIFO and that read leaves one
empty byte position. If a character is waiting in the receive shift
register because the RxFIFO is full, RxFULL is not reset until the
second read of the RxFIFO since the waiting character is
immediately loaded to the RxFIFO.
SR[0] – Receiver Ready (RxRDY)
This bit indicates that a character has been received and is waiting
in the RxFIFO to be read by the CPU. It is set when the character is
transferred from the receive shift register to the RxFIFO and reset
when the CPU reads the RxFIFO, and no more characters are in the
RxFIFO.
comparing to the reference address in ARCR. The bit and interrupt
is negated by a write to the CR with command x11011, Reset
Address Recognition Status.
ISR[4] – Xon/Xoff Status Change
This bit is set when an Xon/Xoff character being received from an
external source. The bit is negated by a read of the channel Xon
Interrupt Status Register, XISR.
ISR[3] – Reserved Always reads a 0
ISR[2] – Change in Channel Break Status
This bit, when set, indicates that the receiver has detected the
beginning or the end of a received break. It is reset when the CPU
issues a reset break change interrupt command via the CR.
ISR[1] – Receiver Ready
The general function of this bit is to indicate that the RxFIFO has
data available. The particular meaning of this bit is programmed by
MR2[3:2]. If programmed as receiver ready(MR2[3:2] = 00), it
indicates that at least one character has been received and is
waiting in the RxFIFO to be read by the host CPU. It is set when the
character is transferred from the receive shift register to the RxFIFO
and reset when the CPU reads the last character from the RxFIFO.
If MR2[3:2] is programmed as FIFO full, ISR[1] is set when a
character is transferred from the receive holding register to the
RxFIFO and the transfer causes the RxFIFO to become full, i.e. all
sixteen FIFO positions are occupied. It is reset when ever RxFIFO
is not full. If there is a character waiting in the receive shift register
because the FIFO is full, the bit is set again when the waiting
character is transferred into the FIFO.
The other two conditions of these bits, 3/4 and half full operate in a
similar manner. The ISR[1] bit is set when the RxFIFO fill level
Bit 1
RxRDY
Receiver has entered
arbitration process
Bit 0
TxRDY
Transmitter has entered
arbitration process
SC28L198
Product data sheet