SC28L194A1A NXP Semiconductors, SC28L194A1A Datasheet - Page 10

• Manufacturer Part Number: SC28L194A1A
• Description: UART Interface IC 3V-5V 4CH UART INTEL/MOT INTRF
• Manufacturer: NXP Semiconductors
• Type: Quad UART for 3.3 V and 5 V supply voltager

Specifications of SC28L194A1A

• Number Of Channels: 4
• Data Rate: 460.8 Kbps
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 3 V
• Supply Current: 30 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Package / Case: PLCC-68
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 3.3 V, 5 V
• Lead Free Status / Rohs Status: Details
• Other names: SC28L194A1A,512

Philips Semiconductors
General Purpose Pins
In addition to the I/O ports for each UART four other ports are
provided which service the entire chip. Two are dedicated as inputs
and two are as outputs. The Gin1 and Gin0 are the input pins; Gout0
and Gout1 the outputs. These ports are multiplexed to nearly every
functional unit in the chip. See the registers which describe the
multitude of connections available for these pins. The Gout0 and
Gout1 pins are highly multiplexed outputs and are controlled by four
(4) registers: GPOSR, GPOR, GPOC and GPOD. The Gin0 and
Gin1 pins are available to the receivers and transmitters, BRG
counters and the Gout0 and Gout1 pins.
Global Registers
The “Global Registers”, 19 in all, are driven by the interrupt system.
These are not real hardware devices. They are defined by the
content of the CIR (Current Interrupt Register) as a result of an
interrupt arbitration. In other words they are indirect registers pointed
to by the content of the CIR. The list of global register follows:
A read of the GRxFIFO will give the content of the RxFIFO that
presently has the highest bid value. The purpose of this system is to
enhance the efficiency of the interrupt system. The global registers
and the CIR update procedure are further described in the Interrupt
Arbitration system
Character Recognition
The character recognition circuits are basically designed to provide
general purpose character recognition. Additional control logic has
been added to allow for Xon/Xoff flow control and for recognition of
the address character in the multi-drop or “wake-up” mode. This
logic also allows for the generation of an interrupts in either the
general purpose recognition mode or the specific conditions
mentioned above.
Xon Xoff Characters
The programming of these characters is usually done individually.
However a method has been provided to write to all of registers in
one operation. There are “Gang Load” and a “Gang Write”
commands provided in the channel A Command Register. When
these commands are executed all registers are programmed with
the same characters. The “write” command loads a used defined
character; the ’load” command loads the standard Xon/Xoff
characters. Xon is x’11; Xoff x’13’. Any enabling of the Xon/Xoff
functions will use the contents of the Xon and Xoff character
registers as the basis on which recognition is predicated.
Multi-drop or Wake-up or 9-bit Mode
This mode is used to address a particular UART among a group
connected to the same serial data source. Normally it is
accomplished by redefining the meaning of the parity bit such that it
indicates a character as address or data. While this method is fully
supported in the SC28L194 it also supports recognition of the
character itself. Upon recognition of its address the receiver will be
enabled and data pushed onto the RxFIFO.
Further the Address recognition has the ability, if so programmed, to
disable (not reset) the receiver when an address is seen that is not
recognized as its own. The particular features of “Auto Wake and
Auto Doze” are described in the detail descriptions below.
2006 Aug 15
Quad UART for 3.3 V and 5 V supply voltage
GIBCR
GICR
GITR
GRxFIFO Pointer to the interrupting receiver FIFO
GTxFIFO Pointer to the interrupting transmitter FIFO
The byte count of the interrupting FIFO
Channel number of the interrupting channel
Type identification of interrupting channel
10
Note: Care should be taken in the programming of the character
recognition registers. Programming x’00, for example, may result in
a break condition being recognized as a control character. This will
be further complicated when binary data is being processed.
Character Stripping
The MR0 register provides for stripping the characters used for
character recognition. Recall that the character recognition may be
conditioned to control several aspects of the communication.
However this system is first a character recognition system. The
status of the various states of this system are reported in the XISR
and ISR registers. The character stripping of this system allows for
the removal of the specified control characters from the data stream:
two for the Xon /Xoff and one for the Wake-up. Via control in the
MR0 register these characters may be discarded (stripped) from the
data stream when the recognition system “sees” them or they may
be sent on the RxFIFO. Whether they are stripped or not the
recognition will process them according to the action requested: flow
control, Wake-up, interrupt generation, etc. Care should be
exercised in programming the stripping option if noisy environments
are encountered. If a normal character was corrupted to an Xoff
character turned off the transmitter and it was then stripped, then the
stripping action could make it difficult to determine the cause of
transmitter stopping.
Interrupt Arbitration and IRQN Generation
Interrupt arbitration is the process used to determine that an
interrupt request should be presented to the host. The arbitration is
carried out between the “Interrupt Threshold” and the “sources”
whose interrupt bidding is enabled by the IMR. The interrupt
threshold is part of the ICR (Interrupt Control Register) and is a
value programmed by the user. The “sources” present a value to the
interrupt arbiter. That value is derived from four fields: the channel
number, type of interrupt source, FIFO fill level, and programmable
value. Only when one or more of these values exceeds the
threshold value in the interrupt control register will the interrupt
request (IRQN) be asserted.
Following assertion of the IRQN the host will either assert
IACKN(Interrupt Acknowledge) or will use the command to “Update
the CIR”. At the time either action is taken the CIR will capture the
value of the source that is prevailing in the arbitration process. (Call
this value the winning bid)
The value in the CIR is the central quantity that results from the
arbitration. It contains the identity of the interrupting channel, the
type of interrupt in that channel (RxD, TxD, COS etc.) the fill levels
of the RxD or TxD FIFOs and , in the case of an RxD interrupt an
indicator of error data or good data. It also drives the Global
Registers associated with the interrupt. Most importantly it drives
the modification of the Interrupt Vector.
The arbitration process is driven by the Sclk. It scans the 10 bits of
the arbitration bus at the Sclk rate developing a value for the CIR
every 22 Sclk cycles. New arbitration values presented to the
arbitration block during an arbitration cycle will be evaluated in the
next arbitration cycle.
For sources other than receiver and transmitters the user may set
the high order bits of an interrupt source’s bid value, thus tailoring
the relative priority of the interrupt sources. The priority of the
receivers and transmitters is controlled by the fill level of their
respective FIFOs. The more filled spaces in the RxFIFO the higher
the bid value; the more empty spaces in the TxFIFO the higher its
priority. Channels whose programmable high order bits are set will
SC28L194
Product data sheet