![](http://datasheet.mmic.net.cn/290000/SC28L194_datasheet_16147734/SC28L194_22.png)
Philips Semiconductors
Preliminary specification
SC28L194
Quad UART for 3.3V and 5V supply voltage
1998 Sep 21
22
Table 9.
Code
Command
CR[7:3]
Description
00011
Reset Transmitter
00100
Reset Error Status
01000
Assert RTSN (I/O2 or I/O1)
01001
Negate RTSN (I/O2 or I/O1)
01100
Set time-out mode off
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Table 10.
SR - Channel Status Register
Bit 7
Bit 6
Bit 5
Received
Break
Error
0 - No
Command Register Code
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01110
Code
CR[7:3]
10011
10100
11000
11001
11100
11110
Command
Description
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01101
Reserved
11101
Gang Write Xoff Character Registers *
Gang Load Xon Character Registers DC1 *
Cancel Transmit X Char command
Reserved
Reset Address Recognition Status
Reserved
Reset All UART channel registers
Reserved
Block Error Status configure
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SR[7] - Received Break
This bit indicates that an all zero character of the programmed
length has been received without a stop bit. Only a single FIFO
position is occupied when a break is received; further entries to the
FIFO are inhibited until the RxD line returns to the marking state for
at least one half bit time (two successive edges of the internal or
external 1x clock). When this bit is set, the change in break bit in the
ISR (ISR[2]) is set. ISR[2] is also set when the end of the break
condition, as defined above, is detected. The break detect circuitry
is capable of detecting breaks that originate in the middle of a
received character. However, if a break begins in the middle of a
character, it must last until the end of the next character in order for
it to be detected.
SR[6] - Framing Error (FE)
This bit, when set, indicates that a stop bit was not detected when
the corresponding data character in the FIFO was received. The
stop bit check is made in the middle of the first stop bit position.
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.
Bit 4
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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.
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.
Bit 3
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1 - Yes
Bit 2
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Bit 1
Bit 0
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Framing Error
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Parity
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Overrun Error
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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.