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Frequently asked questions

16C/68C UART General FAQ

Q What is the difference between your 16CxxB and 68CxxB UART families?
A While they both feature the same 16C core and register settings, the 16C products feature an Intel interface while the 68C products feature a Motorola interface. Additionally, an Intel/Motorola-selectable interface is offered on select 16C products in a 68-pin PLCC (A68) package.
Q What is the operational temperature range for your 16C and 68C UART families?
A Our high-speed 16C and 68C UART families are qualified to operate from -40° to +85° Celsius.
Q In what packages is your high-speed 16C UART family offered?
A Our quad-channel UARTs are offered in 68-pin PLCC and 64-pin LQFP packages. Our dual-channel UARTs are offered in 44-pin PLCC and 48-pin LQFP packages. Our single-channel UARTs are offered in 40-pin DIL, 44-pin PLCC, and 48-pin LQFP packages. Additionally, our SC16C650B and SC16C750B single-channel UARTs and our dual-channel SC16C652B and SC16C752B UARTs are offered in our new ultra-small, 32-pin HVQFN package.
Q In what packages is your high-speed 68C UART family offered?
A Our dual-channel 68C UARTs are offered in 48-pin LQFP packages.
Q Our new design called for the use of a UART running at 57.6Kbps and a supply of 2.5V. Do any of your UARTs meet these requirements?
A All of our 16C and 68C UARTs meet your design requirements. The voltage supply range for these UARTs is from 2.5V to 5.0V. These devices can easily meet your baud rate requirement at all voltages.
Q Do any of your 16C or 68C UARTs have an IrDA interface?
A Our SC16C550, SC16C2550B, SC16C650B, SC16C652B, and SC16C654B UARTs have this interface. Additionally, our SC68C2550B and SC68C652B UARTs also have this capability.
Q Do all your 16C UARTs support software flow control?
A All of our 16C devices with the exception of the SC16C2552 and SC16C750 support single char XON/XOFF flow control.
Q Are your 16C UARTs hardware- and software-compatible to TI and Exar UARTs?
A Our high-speed 16CxxB devices are 100% pin-to-pin hardware-compatible to both TI or Exar parts. Some minor software changes may be required depending on the features used and how the software was written. It has been our experience that most designs operate without any changes to the software. Our Interface Application Notes detail the differences between our devices and Exar devices. We also provide Interface Product and Technical Support by email. To the best of our knowledge, any modifications to software to accommodate NXP devices are compatible with TI or Exar devices.
Q Is there a sample schematic that shows the interface to the ISA bus for a 16C654B?
A We do have a sample schematic which shows the interface to the ISA bus for this particular device. Please contact our Interface Product and Technical Support by email with your request, and we will forward you a copy of the schematic.
Q When will full production parts be available for the 16C550B?
A The 16C550B device is in full production. Our Standard ICs website lists all of the 16C devices currently in full production.
Q We need a UART that runs at 2.5V supply, but our power supply specification shows a +/-10% tolerance. Do your UARTs tolerate such a variation in the supply?
A Our 16CxxB UART family is fully operational with a 2.5V supply +/-10% tolerance.
Q Do you offer a UART that can operate with a different transmit baud rate than the receive baud rate?
A Our 16C UART family does not support independent transmitter and receiver baud rates. Our industrial UARTs (SC26, SC68, and SC28 families) do offer this option. The transmitter can run at a different baud rate than the receiver. You can find more information about our industrial UARTs at our Standard ICs website.
Q Which NXP part crosses to Exar's ST16C550?
A NXP Semiconductors' SC16C550B. For a complete 16C UART cross reference chart, please visit our Standard ICs website. You can also use the search box at our Standard ICs website which performs most cross-references.
Q Do you have a cross to the TL16C752 offered by Texas Instruments?
A Yes, it is the NXP SC16C752B. For a complete 16C UART cross reference chart, please visit our Standard ICs website. You can also use the search box at our Standard ICs website which performs most cross-references.
Q Our handheld device needs a UART to communicate with the PC serial port. Which of your high-speed UARTs do you recommend?
A In your application, we assume that you need a single-channel UART with a low-voltage supply and low current consumption with a power down option. Our SC16C550B should be the one to consider. The device can operate at a 2.5V supply, the current consumption is around 1mA, and the device has a sleep mode where the clock circuitry is shut down. In sleep mode, the part draws less than 500uA.
Q Do you have C sample code that shows us how to set up a UART to communicate with a remote UART?
A Yes, we have sample code. Please contact our Interface Product and Technical Support by email with your request, and we will forward a copy.
Q Do you have a PCI UART?
A We do not currently have any PCI UARTs, but a PCI UART design can be done by bridging the PCI bus to our UART by using a PCI-to-ISA bridge.
Q What is the maximum number of channels available in your 16C UART family?
A The maximum number of UART channels in our 16C family is four. Please visit our Standard ICs website for our current four-channel UARTs. This may change in the future if we see a market requirement for an 8-channel 16C device.
Q Which device has the deepest FIFO in your 16C UART family?
A Our SC16C654B has a 64-byte of FIFO in both transmit and receive directions.
Q What is the fastest baud rate that a 16C or 68C UART can run?
A The maximum baud rate supported by our 16C and 68C UARTs is 5Mbps.
Q What is the highest speed that I can run a UART?
A A UART can run up to 5Mbit/s, but its actual speed is limited by the line driver. For RS-232, this is about 1Mbit/s, and for IrDA, this is 112.5Kbit/s.
Q What are the advantages of your 16C and 68C UARTs?
A Our 16C and 68C UARTs operate down to 2.5V, offer a faster bus cycle time, operate at industrial temperatures, have deeper FIFOs, have lower sleep currents, and operate at baud rate of up to 5Mbps.
Q What are the advantages of a standalone UART over an integrated UART?
A Standalone 16C or 68C UARTs have more advanced features than integrated UARTs. The features are deeper FIFOs, faster baud rates, a lower sleep current, hardware and software flow control, and IrDA support.
Q Can a UART work with a microcontroller?
A Yes, a UART can work with a microcontroller such as the 8051, or others, which have a data and address bus for the UART.
Q With what types of CPU can I interface a UART?
A We have UARTs that can work with Intel bus interfaces, Motorola bus interfaces, or both. Our 16C UARTs all have Intel interfaces. Our 68C UARTs all have Motorola interfaces. Select 16C UARTs in a 68-pin PLCC (A68) package feature an Intel/Motorola-selectable interface.
Q How many channels do your UARTs have?
A We offer UART products containing from 1 channel up to 8 channels.
Q What is the bus cycle time when using a 3.3V power supply?
A About 43ns.
Q What UART packages should I look for if small size is important?
A We have select UARTs available in TSSOP and HVQFN which are our smallest packages.

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