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PDF XR19L220 Data sheet ( Hoja de datos )
| Número de pieza | XR19L220 | |
| Descripción | SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER | |
| Fabricantes | Exar Corporation | |
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XR19L220
SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
OCTOBER 2006
REV. 1.0.0
GENERAL DESCRIPTION
The XR19L220 (L220) is a highly integrated device that
combines a full-featured single channel Universal
Asynchronous Receiver and Transmitter (UART) and an
RS-232 transceiver. The L220 is designed to operate with a
single 3.3V or 5V power supply. The L220 is fully compliant
with EIA/TIA-232-F Standards from a +3.0V to +5.5V power
supply. The device operates at 250 Kbps data rate with
worst case 3K ohms load. Both RS-232 driver outputs and
receiver inputs can operate in harsh electrical environments
of +/-15V without damage and can survive multiple +/-15kV
ESD on the RS-232 lines, while maintaining RS-232 output
levels.
The L220 operates in four different modes: Active, Partial
Sleep, Full Sleep and Power-Save. Each mode can be
invoked via hardware or software. In the Active mode, all
functions are active. In the Partial Sleep mode, the internal
crystal oscillator of the UART or charge pump of the RS-
232 transceiver is turned off. In Full Sleep mode, the
internal crystal oscillator and the charge pump is turned off.
In the Power-Save mode, the core logic is isolated from the
control signals (chip select, read/write strobes, address and
data bus lines) to further reduce the power consumption. All
the RS-232 receivers remain active in any of these four
modes.
APPLICATIONS
• Battery-Powered Equipment
• Handheld and Mobile Devices
• Handheld Terminals
• Industrial Peripheral Interfaces
• Point-of-Sale (POS) Systems
FEATURES
• Meets true EIA/TIA-232-F Standards from +3.0V to +5.5V
operation
• Up to 250 Kbps data transmission rate
• 45us sleep mode exit (charge pump to full power)
• ESD protection for RS-232 I/O pins at
■ +/-15kV - Human Body Model
■ +/-15kV - IEC 1000-4-2, Air-Gap Discharge
■ +/- 8kV - IEC 1000-4-2, Contact Discharge
• Software compatible with industry standard 16550 UART
• Intel/Motorola bus select
• Complete modem interface
• Sleep and Power-save modes to conserve battery power
• Wake-up interrupt upon exiting low power modes
FIGURE 1. BLOCK DIAGRAM
PwrSave
A2:A0
D7:D0
IOR#
IOW# (R/W#)
CS#
INT (IRQ#)
RESET (RESET#)
I/M#
*5 V
Tolerant
Inputs
Crystal
Osc/Buffer
BRG
16 Byte
TX FIFO
16 Byte
RX FIFO
Modem
I/Os
TX
RX
RTS#
DTR#
CTS#
DSR#
RI#
CD#
UART
XR19L220
Charge Pump
5K
5K
5K
5K
5K
RS-232 Transceiver
VREF+
VREF-
TXD
RXD
RTS
DTR
CTS
DSR
RI
CD
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com
1 page  
XR19L220
REV. 1.0.0
SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
1.0 PRODUCT DESCRIPTION
The XR19L220 interface converter consists of a full-functional UART with 16 bytes of transmit and receive
FIFO, a charge pump, three RS-232 drivers, five RS-232 receivers, and a sleep/Power-Save mode circuitry. It
operates from a single +3V to 5.5V supply at 250Kbps data rate, while meeting all EIA RS-232F specifications.
Its feature set is fully compatible to the XR16L580 device. Unlike the XR16L580, the modem signals are not
CMOS/TTL level, but conform to EIA/TIA 232 or RS-232 voltage levels. The configuration registers set is
16550 UART compatible for control, status and data transfer. Also, the L220 has 16-bytes of transmit and
receive FIFOs, automatic RTS/CTS hardware flow control, automatic Xon/Xoff and special character software
flow control, transmit and receive FIFO trigger levels, and a programmable baud rate generator with a
prescaler of divide by 1 or 4. Additionally, the L220 includes the ACP pin which the user can shut down the
charge pump for the RS-232 drivers when the L220 is already in sleep mode. The Power-Save feature further
isolates the databus interface to further reduce power consumption in the sleep mode. The L220 is fabricated
using an advanced CMOS process.
Enhanced Features
The L220 UART provides a solution that supports 16 bytes of transmit and receive FIFO memory. The L220 is
designed to work with low supply voltage and high performance data communication systems that require fast
data processing time. Increased performance is realized in the L220 by the transmit and receive FIFOs, FIFO
trigger level controls and automatic flow control mechanism. This allows the external processor to handle more
networking tasks within a given time. This increases the service interval giving the external CPU additional time
for other applications and reducing the overall UART interrupt servicing time. In addition, the L220 provides the
Power-Save mode that drastically reduces the power consumption when the device is not used. The
combination of the above greatly reduces the CPU’s bandwidth requirement, increases performance, and
reduces power consumption. Finally, since the L220 includes an RS-232 transceiver and a full-modem
interface, it can be connected to an RS-232 serial cable directly.
Intel or Motorola Data Bus Interface
The L220 provides a host interface that supports Intel or Motorola microprocessor (CPU) data bus interface.
The Intel bus compatible interface allows direct interconnect to Intel compatible type of CPUs using IOR#,
IOW# and CS# inputs for data bus operation. The Motorola bus compatible interface instead uses the R/W#
and CS# signals for data bus transactions. See pin description section for details on all the control signals. The
Intel and Motorola bus interface selection is made through the pin, I/M#.
Data Rate
The L220 is capable of operation up to 250Kbps data rate using the 16X internal sampling clock rate. The
UART section can operate at much higher speeds, but the speed of the RS-232 transceiver is limited to
250Kbps beyond which the L220 cannot comply with the EIA/TIA-232 electrical characteristics. The device can
operate either with a crystal on pins XTAL1 and XTAL2, or external clock source on XTAL1 pin.
Internal Enhanced Register Sets
The L220 UART has a set of enhanced registers providing control and monitoring functions. Interrupt enable/
disable and status, FIFO enable/disable, selectable TX and RX FIFO trigger levels, automatic hardware/
software flow control enable/disable, programmable baud rates, modem interface controls and status, sleep
mode and mode are all standard features. Following a power on reset or an external reset (and operating in 16
or Intel Mode), the registers defaults to the reset condition and is compatible with the XR16L580.
RS-232 Interface
The L220 includes RS-232 drivers/receivers for the entire modem interface. This feature eliminates the need
for an external RS-232 transceiver. The charge pump provides output voltages of +5V and -5V for its drivers
over the 3.0V to 5.5V VCC supply voltage. The serial outputs TX, RTS and DTR swing between -5V (inactive)
and 5V (active) RS-232 voltage levels. The serial inputs RX, CTS, DSR, CD and RI are RS-232 receivers and
can take any voltage swing from -15V to +15V. The receivers are always active, even in Full Sleep and Power-
Save modes. The RS-232 drivers guarantee a data rate of 250Kbps even when fully loaded with 3Kohm in
parallel with 1000pF load. Also, the slew rate of the driver output is internally limited to a maximum of 30V/us in
order to meet the EIA-232F standard.
5
5 Page 
XR19L220
REV. 1.0.0
SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
upon receiving a character or delay until it reaches the FIFO trigger level. Furthermore, data delivery to the
host is guaranteed by a receive data ready time-out interrupt when data is not received for 4 word lengths as
defined by LCR[1:0] plus 12 bits time. This is equivalent to 3.7-4.6 character times. The RHR interrupt is
enabled by IER bit-0.
2.11.1 Receive Holding Register (RHR) - Read-Only
The Receive Holding Register is an 8-bit register that holds a receive data byte from the Receive Shift
Register. It provides the receive data interface to the host processor. The RHR register is part of the receive
FIFO of 16 bytes by 11-bits wide, the 3 extra bits are for the 3 error tags to be reported in LSR register. When
the FIFO is enabled by FCR bit-0, the RHR contains the first data character received by the FIFO. After the
RHR is read, the next character byte is loaded into the RHR and the errors associated with the current data
byte are immediately updated in the LSR bits 2-4.
FIGURE 8. RECEIVER OPERATION IN NON-FIFO MODE
16X Clock
Receive Data Shift Data Bit
Register (RSR)
Validation
Receive Data Characters
Receive
Data Byte
and Errors
Error
Tags in
LSR bits
4:2
Receive Data
Holding Register
(RHR)
RHR Interrupt (ISR bit-2)
RXFIFO1
FIGURE 9. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE
16X Clock
16 bytes by 11-bit
wide
FIFO
Receive Data
Byte and Errors
Receive Data Shift
Register (RSR)
Receive
Data FIFO
Receive
Data
Data Bit
Validation
Receive Data Characters
Example
:
RX FIFO trigger level selected at 8 bytes
Data falls to
4
RTS# re-asserts when data falls below the flow
control trigger level to restart remote transmitter.
Enable by EFR bit-6=1, MCR bit-1.
FIFO Trigger=8 RHR Interrupt (ISR bit-2) programmed for
desired FIFO trigger level.
FIFO is Enabled by FCR bit-0=1
Data fills to
14
RTS# de-asserts when data fills above the flow
control trigger level to suspend remote transmitter.
Enable by EFR bit-6=1, MCR bit-1.
RXFIFO1
11
11 Page | ||
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| PDF Descargar | [ Datasheet XR19L220.PDF ] | |
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