SC28L202A1DGG,118 NXP Semiconductors, SC28L202A1DGG,118 Datasheet - Page 15
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SC28L202A1DGG,118
Manufacturer Part Number
SC28L202A1DGG,118
Description
IC UART DUAL W/FIFO 56-TSSOP
Manufacturer
NXP Semiconductors
Series
IMPACTr
Datasheet
1.SC28L202A1DGG118.pdf
(77 pages)
Specifications of SC28L202A1DGG,118
Features
False-start Bit Detection
Number Of Channels
2, DUART
Fifo's
256 Byte
Voltage - Supply
3.3V, 5V
With Parallel Port
Yes
With Auto Flow Control
Yes
With False Start Bit Detection
Yes
With Modem Control
Yes
With Cmos
Yes
Mounting Type
Surface Mount
Package / Case
56-TFSOP (0.240", 6.10mm Width)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
935276109118
SC28L202A1DGG-T
SC28L202A1DGG-T
SC28L202A1DGG-T
SC28L202A1DGG-T
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
SC28L202A1DGG,118
Manufacturer:
EPCOS
Quantity:
12 000
Philips Semiconductors
encodes the number of empty positions for presentation to the
interrupt arbitration system. The encoding value is the number of
empty positions. Thus, an empty TxFIFO will bid with the value or
255; when full it will not bid at all; one position empty bids with the
value 0. A Full TxFIFO will not bid since no character is available.
Normally TxFIFO will present a bid to the arbitration system
whenever it has one or more empty positions. The Bits of the
TxFIFO Interrupt Level in the MR0(5:4) allow the user to modify this
characteristic so that bidding will not start until one of four levels
(one or more filled, empty, 16 filled, 240 filled, full) have been
reached. As will be shown later this feature may be used to make
moderate improvements in the interrupt service efficiency. A similar
system exists for the Receiver.
Transmitter
The 28L202 is conditioned to transmit data when the transmitter is
enabled through the command register. The transmitter of the
28L202 indicates to the CPU that it is ready to accept a character by
setting the ISR TxRDY bit in the status register. This condition can
be programmed to generate an interrupt request at I/O4 or IRQN.
When the transmitter is initially enabled the TxRDY and Tx Idle bits
will be set in the status register. When a character is loaded to the
transmit FIFO the Tx Idle bit will be reset. The Tx Idle bit will not set
until the transmit FIFO is empty and the transmit shift register has
finished transmitting the stop bit of the last character written to the
transmit FIFO.
The TxRDY bit is set whenever the transmitter is enabled and the
TxFIFO is not full. Data is transferred from the holding register to
transmit shift register when it is idle or has completed transmission
of the previous character. Characters cannot be loaded into the
TxFIFO while the transmitter is disabled.
The transmitter converts the parallel data from the CPU to a serial
bit stream on the TxD output pin. It automatically sends a start bit
followed by the programmed number of data bits, an optional parity
bit, and the programmed number of stop bits. The least significant
bit is sent first. Following the transmission of the stop bits, if a new
character is not available in the TxFIFO, the TxD output remains
High and the Tx Idle bit in the Status Register (SR) will be set to 1.
Transmission resumes and the Tx Idle bit is cleared when the CPU
loads a new character into the TxFIFO.
If the transmitter is disabled, it continues operating until the
character currently being transmitted is completely sent out. The
transmitter can be forced to send a continuous Low condition by
issuing a send break command. The transmitter can be reset
through a software command. If it is reset, operation ceases
immediately and the transmitter must be enabled through the
command register before resuming operation.
If CTS option of hardware flow control is enabled (MR2 [4] = 1), the
CTS input at I/O0 or I/O1 must be Low in order for the character to
be transmitted. The transmitter will check the state of the CTS input
at the beginning of each character transmitted. If it is found to be
High, the transmitter will delay the transmission of any following
characters until the CTS has returned to the low state. CTS going
high during the serialization of a character will not affect that
character.
It is an interesting point of the I/O system inputs being always active
that by enabling transmitter to be sensitive the I/O0 or I/O1 and then
controlling the I/O pin as an out put that one is able to control the
transmitter flow via software control of the I/O pin.
The transmitter can also control the RTSN outputs, I/O0 or I/O1 via
MR2 [5]. When this mode of operation is set (often referred to as the
2005 Nov 01
Dual UART
9
RS-485 method) the meaning of the I/O0 B or I/O1 B signals is ‘all
bytes loaded to the transmitter’s FIFO have been transmitted
including the last stop bit(s). See the MR2(5) description for enabling
this automatic function.
Receiver Operation
Receiver
The receiver accepts serial data on the RxD pin, converts the serial
input to parallel format, checks for start bit, stop bit, parity bit (if any),
framing error or break condition, and presents the assembled
character and its status condition to the CPU via the RxFIFO. Three
status bits are FIFOed with each character received. The RxFIFO is
really 11 bits wide: eight data and 3 status. Unused FIFO bits for
character lengths less than 8 bits are set to zero.
It is important to note that in the asynchronous protocol the receiver
logic considers the entire message to be contained within the start
bit to the stop bit. It is not aware that a message may contain many
characters. The receiver returns to its idle mode at the end of each
stop bit! As described below it immediately begins to search for
another start bit, which is normally, of course, immediately
forthcoming.
1x and 16x mode, Receiver
The receiver operates in one of two modes: 1x and 16x. Of the two,
the 16x is more robust and the preferred mode. Although the 1x
mode may allow a faster data rate is does not provide for the
alignment of the receiver 1x data clock to that of the transmitter. This
strongly implies that the 1x clock of the remote transmitter is
available to the receiver; the two devices are physically close to
each other.
The 16x mode operates the receiver logic at a rate 16 times faster
than the 1x data rate. This allows for validation of the start bit length,
the validation of level changes at the receiver serial data input
(RxD), and the validation of the stop bit length. Of most importance
in the 16x mode is the ability of the receiver logic to align the phase
of the internally generated receiver 1x data clock to that of the
received start bit of the remote transmitter. This occurs with an
accuracy of less than 1/16 bit time.
Receiver
The receiver of the 28L202 is conditioned to receive data when
enabled through the command register. The receiver looks for a
High-to-Low (mark-to-space) transition of the start bit on the RxD
input pin. If a transition is detected, the state of the RxD pin is
sampled each 16X clock for 7-1/2 clock periods (16X clock mode) or
at the next rising edge of the bit time clock (1X clock mode). If RxD
is sampled high, (that is the start bit was low less than 7/16 to
time) the start bit is judged invalid and the search for another valid
start bit begins immediately. If RxD is still low, a valid start bit is
assumed and the receiver then continues to sample the input at
one-bit time intervals at the theoretical center of the bit. When the
proper number of data bits and parity bit (if used) have been
assembled, and one half-stop bit has been detected the receiver
loads the byte to the FIFO. The least significant bit is received first.
The data is then transferred to the Receive FIFO and the ISR
RxRDY bit in the SR is set to a 1. This condition can be
programmed to generate an interrupt at IRQN or I/O[4:5] for
channels A or B respectively. If the character length is less than 8
bits, the most significant unused bits in the RxFIFO are set to zero.
After the stop bit is detected, the receiver will immediately look for
the next start bit. However, if a non-zero character was received with
the stop bit at a zero level (framing error) and RxD remains Low for
at least another one half bit time after the stop bit was sampled, then
SC28L202
Product data sheet
bit