XR20M1280

I2C/SPI UART with 128-Byte FIFO and Integrated Level Shifters
Data Sheet

Description

The XR20M1280¹ (M1280) is a single-channel I2C/SPI Universal Asynchronous Receiver and Transmitter (UART) with integrated level shifters and 128 bytes of transmit and receive FIFOs.

For flexibility in a mixed voltage environment, the M1280 has 4 VCC pins. There is a VCC pin for the core, a VCC pin for the UART signals, a VCC pin for the CPU interface signals and a VCC pin for the GPIO signals. The VCC pins for the UART, GPIO and I2C/SPI interface signals allow for the M1280 to interface with devices operating at different voltage levels eliminating the need for external voltage level shifters. The VCC core voltage helps to lower the overall power consumption for applications that use slower data rates.

The Auto RS-485 Half-Duplex Direction control feature simplifies both the hardware and software for half-duplex RS-485 applications. In addition, the Multidrop mode with Auto Address detection and Address Byte Control features increase the performance by simplifying the software routines.

The Independent TX/RX Baud Rate Generator feature allows the transmitter and receiver to operate at different baud rates. In addition, the Fractional Baud Rate Generator feature provides flexibility for crystal/clock frequencies for generating standard and non-standard baud rates.

The M1280 has programmable transmit and receive FIFO trigger levels, automatic hardware and software flow control, and data rates of up to 24 Mbps. Power consumption of the M1280 can be minimized by enabling the sleep mode.

The M1280 has a 16550 compatible register set that provide users with operating status and control, receiver error indications, and modem serial interface controls. An internal loopback capability allows onboard diagnostics. The M1280 has a selectable I2C/SPI bus interface.

NOTE: ¹Covered by U.S. Patent #5,649,122.

Features

  • Integrated Level Shifters on CPU interface, UART and GPIO signals
  • Selectable I2C/SPI bus interface
  • 26MHz maximum SPI clock
  • 24Mbps maximum UART data rate
  • Up to 16 GPIOs
  • 128-Bytes TX and RX FIFOs
  • Programmable TX/RX trigger levels
  • TX/RX FIFO Level Counters
  • Independent TX/RX Baud Rate Generator
  • Fractional Baud Rate Generator
  • Auto RTS/CTS Hardware Flow Control
  • Auto XON/XOFF Software Flow Control
  • Auto RS-485 Half-Duplex Direction Control
  • Multidrop mode w/ Auto Address Detect (RX)
  • Multidrop mode w/ Address Byte Control (TX)
  • Sleep Mode with Automatic Wake-up
  • Infrared (IrDA 1.0 and 1.1) mode
  • 1.62V to 3.63V supply operation
  • Crystal oscillator or external clock input
  • 5V tolerant inputs

Application

  • Personal Digital Assistants (PDAs)
  • Cellular Phones/Data Devices
  • Battery-Operated Devices
  • Global Positioning System (GPS)
  • Bluetooth

Download Software Drivers

Design Tools

Evaluation Hardware and Software
Operating System Driver Version Release Date File
Linux 3.x.x 1.0.0 March 2015

Packaging

Pkg Code Details Quantities Dimensions PDF
QFN24 4x4 OPT1
  • JEDEC Reference: MO-220
  • MSL Pb-Free: L2 @ 260
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 39.2
  • Bulk Pack Style: Tray
  • Quantity per Bulk Pack: 490
  • Quantity per Reel: 3000
  • Quantity per Tube: n/a
  • Quantity per Tray: 490
  • Reel Size (Dia. x Width x Pitch): 330 x 12 x 8
  • Tape & Reel Unit Orientation: Quadrant 1
  • Dimensions: mm
  • Length: 4.0
  • Width: 4.0
  • Thickness: 1.00
  • Lead Pitch: 0.5
QFN32 5x5 OPT3
  • JEDEC Reference:
  • MSL Pb-Free: L2 @ 260ºC
  • MSL SnPb Eutectic:
  • ThetaJA: 30
  • Bulk Pack Style: Tray
  • Quantity per Bulk Pack: 490
  • Quantity per Reel: 3000
  • Quantity per Tube: n/a
  • Quantity per Tray: 490
  • Reel Size (Dia. x Width x Pitch): 330 x 12 x 8
  • Tape & Reel Unit Orientation: Quadrant 1
  • Dimensions: mm
  • Length: 5
  • Width: 5
  • Thickness: 1.00
  • Lead Pitch: 0.5

Parts & Purchasing

Part Number Pkg Code RoHS Min Temp Max Temp Status Buy Now Order Samples
XR20M1280IL24-F QFN24 4x4 OPT1 -40 85 Active Order
XR20M1280IL24TR-F QFN24 4x4 OPT1 -40 85 Active Order
XR20M1280IL32-F QFN32 5x5 OPT3 -40 85 Active Order
XR20M1280IL32TR-F QFN32 5x5 OPT3 -40 85 OBS Suggested:
XR20M1280IL32-F
XR20M1280IL40-F QFN40 6x6 -40 85 OBS Suggested:
XR20M1280IL32-F
XR20M1280IL40TR-F QFN40 6x6 -40 85 OBS Suggested:
XR20M1280IL32-F
XR20M1280L24-0A-EB Board Active
XR20M1280L24-0B-EB Board Active
XR20M1280L32-0A-EB Board Active
XR20M1280L32-0B-EB Board Active
XR20M1280L40-0B-EB Board Active
Show obsolete parts
Part Status Legend
Active - the part is released for sale, standard product.
EOL (End of Life) - the part is no longer being manufactured, there may or may not be inventory still in stock.
CF (Contact Factory) - the part is still active but customers should check with the factory for availability. Longer lead-times may apply.
PRE (Pre-introduction) - the part has not been introduced or the part number is an early version available for sample only.
OBS (Obsolete) - the part is no longer being manufactured and may not be ordered.
NRND (Not Recommended for New Designs) - the part is not recommended for new designs.

Quality Documents

Part Number REACH
XR20M1280IL24-F Download
XR20M1280IL32-F Download
XR20M1280IL24TR-F Download
Additional Quality Documentation may be available, please contact customersupport@maxlinear.com.
Distribution Date Description File
07/11/2017 Product Discontinuation Notification
01/27/2017 Qualification of alternate assembly subcon, ANST, China.
04/02/2014 Qualified UTAC Thailand for assembly using copper wire or gold wire bonding assembly, in addition to the current qualified gold wire bonding assembly sites, Unisem Batam and UTAC China. Material change and alternate assembly site.
08/10/2011 Material change and a new assembly & test supplier (ASE, Kunshan). Business consolidation.

Frequently Asked Questions

For some UARTs, Microsoft certified drivers are available for Windows Operating System and can be downloaded via Windows Update. These drivers and others, including for Linux and other Operating Systems can be found by visiting https://www.exar.com/design-tools/software-drivers Please note Software Driver Use Terms.

 

 
You can also get to this link by going to the exar.com website, clicking on Support (in black bar near top of page), then click on Design Tools, then under Evaluation Hardware and Software (towards right of page) click on Software Drivers.
 
 

Click on the version link under Driver Version of the desired type of UART, part number and operating system. A zip file is downloaded which contains a ReadMe file with instructions.

Links to datasheets and product family pages are in the software driver table for easy reference. 

Typically, this device will be used in an application with a microcontroller that has either an SPI or I2C interface. There should already be some sample code for communicating with a device on the I2C or SPI bus. The microcontroller will just need to provide the appropriate address or CS# to communicate with the I2C/SPI UART.

There is a pin to select between the I2C and the SPI mode. The pin is connected to VCC to select the I2C mode and connected to GND to select the SPI mode.

By default, the GPIOs are in the input state so they must be connected to VCC or GND, or they must be set as outputs after power-up. If they are set as outputs after power-up, then there will be extra current as the GPIOs are floating.

Our evaluation boards have the UART, a transceiver (RS-232, RS-485/422 or IR), a connector for the transceiver, and some test points for either the I2C or the SPI signals to interface directly with a microcontroller with an I2C or an SPI interface.

LSR bit-6 is a superset of LSR bit-5. The transmitter consists of a TX FIFO (or THR only when FIFOs are not enabled) and a Transmit Shift Register (TSR). When LSR bit-5 is set, it indicates that the TX FIFO (or THR) is empty, however there may be data in the TSR. When LSR bit-6 is set, it indicates that the transmitter (TX FIFO + TSR) is completely empty.

You can tell by reading LSR bit-5 or bit-6. If they are '0', then the transmit interrupt was generated by the trigger level. If they are '1', then the transmit interrupt was generated by the TX FIFO becoming empty. For enhanced UARTs, you can just read the FIFO level counters.

An RX Data Ready interrupt is generated when the number of bytes in the RX FIFO has reached the RX trigger level. An RX Data Timeout interrupt is generated when the RX input has been idle for 4 character + 12 bits time.

For some UARTs, the RX Data Timeout interrupt has a higher priority and in others, the RX Data Ready interrupt has a higher priority. See the interrupt priority section of the datasheet.

The UART requires a clock and a valid baud rate in order to transmit and receive data. Check that there is a clock signal on the XTAL1 input pin. Also, valid divisors need to be written into the DLL and DLM registers. Most UARTs have random (invalid) values upon power-up.

For most UARTs, the interrupt is generated when the data is ready to be read from the RX FIFO. The are some UARTs that generate the interrupt when the character with the error is received. There are some UARTs that have a register bit to select whether the LSR interrupt is generated immediately or delayed until it is ready to be read.

The UART will enter the sleep mode if the following conditions have been satisfied for all channels:
 
-Sleep Mode is enabled
-No interrupts are pending
-TX and RX FIFOs are empty
-RX input pin is idling HIGH (LOW in IR mode)
-Valid values in DLL and DLM registers
-Modem input pins are idle (MSR bits 3-0=0x0)
 
See AN204, UART Sleep Mode for more information on UART Sleep Mode

The UART will wake-up from sleep mode by any of the following conditions on any channel:
 
-Sleep mode is disabled
-Interrupt is generated
-Data is written into THR
-There is activity on the RX input pin
-There is activity on the modem input pins
 
If the sleep mode is still enabled and all wake-up conditions have been cleared, it will return to the sleep mode.
 
See AN204, UART Sleep Mode for more information on UART Sleep Mode 

There will be no activity on the XTAL2 output.
 
See AN204, UART Sleep Mode for more information on UART Sleep Mode 

For any UART that has the wake-up indicator interrupt, an interrupt will be generated when the UART wakes up even if no other interrupts are enabled.
 
See AN204, UART Sleep Mode for more information on UART Sleep Mode 

No, Auto RTS and Auto CTS are independent. Auto RTS is toggled by the UART receiver. Auto CTS is monitored by the UART Transmitter.

No, Auto RTS and Auto CTS will work normally without the interrupts enabled.

No, software flow control characters are not loaded into the RX FIFO.

Since 2-character software flow control requires that 2 consecutive flow control characters match before data transmission is stopped or resumes, there is less of a chance that data transmission is stopped because one data byte matched a control character.

Auto RS485 Half-Duplex Control feature overrides the Auto RTS flow control feature if both features use the RTS# output pin. Both features can only be used simultaneously if the Auto RS485 control output is not the RTS# output. For some UARTs, the Auto RS485 control output is not the RTS# output.

The polarity of the RS485 control output varies from one UART to another. For some UARTs, an inverter may be required. Some of the newer UARTs have register bits that can change that polarity of the RS485 control output.

In the normal mode, the TX interrupt is generated when the TX FIFO is empty, and there may still be data in the Transmit Shift Register. In the RS485 mode, the TX interrupt is generated when the TX FIFO and the TSR register are both empty.

It is recommended that the FIFO counters at the Scratchpad Register location be used. When transmitting or receiving data, writing to the LCR register could result in transmit and/or receive data errors.

Due to the dynamic nature of the FIFO counters, it is recommended that the FIFO counter registers be read until consecutive reads return the same value.

All of the UARTs that have the IR mode supports up to 115.2Kbps as specified in IrDA 1.0. The newer I2C/SPI UARTs can support up to 1.152Mbps as specified in IrDA 1.1.

No, it just has to meet the minimum high and low pulse widths.

Find the product page of the part that you want to get an evaluation board for and click on Parts & Purchasing. Example:

 

Find the icons under Buy Now or Order Samples:

 
 

Click on the Buy Now icon and see who has stock and click on the Buy button:

 
 
 

Alternatively, you can click on the Order Samples

 
 

If the icons are missing, then contact Customer Support.

The -F suffix indicates ROHS / Green compliance:
https://www.exar.com/quality-assurance-and-reliability/lead-free-program

The best way to determine this is to go to maxlinear.com and type the part into the search function. At or near the top of the results you should see something that looks like:
 
 
 

In this example, we looked for XRA1201. Click on part number header or on the link at the bottom of the result.  This brings you to the product page. For example:

 
 
 

Click on Parts & Purchasing, highlighted with the blue arrow above. The screen changes to:

 
 
 

Notice the status column and the “Show obsolete parts” link.  A legend tells you the definition of the different statuses. Click on the “Show obsolete parts” link to see EOL or OBS part numbers along with the Active part numbers, the legend still present:

 
 
 

Another method to find out if a part is OBS or EOL is to click on SUPPORT at the top:

 
 
 

And then Product Change Notifications:

 
  
 

Type the part into the search, and click on one of the part numbers from the drop down menu. Then you can look for the Product Discontinuation Notice, which generally is at the top of the list, for example:

 
 
 

If you see this, it tells you that this particular orderable part has been discontinued and when the last order date is, or was. If you click on the file, then you can view the notice we sent about this if you purchased the part in the recent past. It may also advise of a replacement part. When an orderable part first becomes discontinued, Product Discontinuation Notices are sent are sent to those who have purchased the parts in the recent past, if purchased directly, with a dated opportunity to place a last order.

It depends on the baud rate. For example, for a start bit, 8 data bits, no stop bit and 1 stop bit, the maximum baud rate deviation is 4.76%. For more information, see https://www.exar.com/appnote/dan108.pdf

Please check that all the following conditions are satisfied first.

 

  • no interrupts pending (ISR bit-0 = 1)
  • modem inputs are not toggling (MSR bits 0-3 = 0)
  • RX input pin is idling HIGH • divisor (the value in DLL register) is non-zero
  • TX and RX FIFOs are empty

 

Be sure sleep mode bit has been set to 1. If there are multiple UART channels, the sleep conditions must be true for all channels.

 

See more on Sleep Mode in AN204 UART Sleep Mode.

Yes. Note: some devices do have powersave mode. If UART goes into powersave mode, then the registers are not accessible.

 

See more on Sleep Mode in AN204 UART Sleep Mode.

Read LSR register to check whether the UART receives the data or not.

 

  • If LSR value is 0x60, it means that either UART receiver FIFO doesn’t receive the data or the data in receiver FIFO has been read out before the read of LSR.
  • If LSR value is 0x00, it means data is still in the THR (clock doesn’t oscillate to transmit data).
  • If LSR value is 0xFF, it means either UART is in powersave mode or UART is powered off. For those devices with powersave mode, be sure that UARTS are not in powersave mode.

 

 

See more on Sleep Mode in AN204 UART Sleep Mode.

 

  • Check whether the register set can be accessed.
  • Check whether the crystal is oscillating fully.
  • Check whether the data can be transmitted in internal loopback mode.

 

 

See more on Sleep Mode in AN204 UART Sleep Mode.