Dual UART with 16-Byte Transmit and Receive FIFOs


The ST16C2550 (2550) is a dual universal asynchronous receiver and transmitter (UART). The ST16C2550 is an improved version of the NS16C550 UART with higher operating speed and ower access time. The 2550 provides enhanced UART functions with 16 byte FIFO’s, a modem control interface, and data rates up to 1.5Mbps. Onboard status registers provide the user with error indications and operational status. System interrupts and modem control features may be tailored by external software to meet specific user requirements.

An internal loop-back capability allows onboard diagnostics. Independent programmable baud rate generators are provided to select transmit and receive clock rates from 50 Bps to 1.5 Mbps. The Baud rate generator can be configured for either crystal or external clock input.

The ST16C2550 is available in a 40-pin plastic-DIP, 44-pin PLCC, and 48-pin TQFP packages. The 40 pin package does not offer TXRDY and RXRDY pins (DMA Signal monitoring). Otherwise the three package versions are the same. The ST16C2550 is functionally compatible with the ST16C2450. The ST16C2550 is fabricated in an advanced CMOS process to achieve low drain power and high speed requirements.

For UART technical support or to obtain an IBIS model for this product, please email Exar's UART Technical Support group.

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  • Dual UART device
  • Pin and functionally compatible to ST16C2450 and software compatible with INS8250, NS16C550
  • Up to 4 Mbps with external clock of 64 MHz
  • Up to 1.5Mbps data rate with a 24MHz crystal frequency
  • 16 byte transmit FIFO to reduce the bandwidth requirement of the external CPU.
  • 16 byte receive FIFO with error flags to reduce the bandwidth requirement of the external CPU
  • Independent transmit and receive UART control
  • Four selectable Receive FIFO interrupt trigger levels
  • Modem control signals (-CTS, -RTS, -DSR, -DTR, -RI, -CD, and Software controllable line break)
  • Programmable character lengths (5, 6, 7, 8) with Even, odd, or no parity
  • Status report register
  • Crystal or external clock input
  • TTL compatible inputs, outputs
  • 3.3V or 5V supply operation
  • Pb-Free, RoHS Compliant Versions Offered


  • Portable Appliances
  • Telecommunication Network Routers
  • Ethernet Network Routers
  • Cellular Data Devices
  • Factory Automation and Process Controls

Design Tools

Simulation Models
Evaluation Hardware and Software


Pkg Code Details Quantities Dimensions PDF
  • JEDEC Reference: MS-011
  • MSL Pb-Free: n/a
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 50.0ºC/W
  • Bulk Pack Style: Tube
  • Quantity per Bulk Pack: n/a
  • Quantity per Reel: n/a
  • Quantity per Tube: 9
  • Quantity per Tray: n/a
  • Reel Size (Dia. x Width x Pitch): n/a
  • Tape & Reel Unit Orientation: n/a
  • Dimensions: inch
  • Length: 2.100 max.
  • Width: 0.580 max.
  • Thickness: 0.195 max.
  • Lead Pitch: 0.100
  • JEDEC Reference: MS-018
  • MSL Pb-Free: L1 @ 260ºC
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 38.0ºC/W
  • Bulk Pack Style: Tube
  • Quantity per Bulk Pack: n/a
  • Quantity per Reel: 500
  • Quantity per Tube: 27
  • Quantity per Tray: n/a
  • Reel Size (Dia. x Width x Pitch): 330 x 32 x 24
  • Tape & Reel Unit Orientation: Pin 1 at sprocket hole.
  • Dimensions: inch
  • Length: 0.653
  • Width: 0.653
  • Thickness: 0.152
  • Lead Pitch: 1.27
  • JEDEC Reference: MO-026
  • MSL Pb-Free: L3 @ 260ºC
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 59.0ºC/W
  • Bulk Pack Style: Tray
  • Quantity per Bulk Pack: n/a
  • Quantity per Reel: 1500
  • Quantity per Tube: n/a
  • Quantity per Tray: 250
  • Reel Size (Dia. x Width x Pitch): 330 x 16 x 12
  • Tape & Reel Unit Orientation: Pin 1 at sprocket hole.
  • Dimensions: mm
  • Length: 7.0
  • Width: 7.0
  • Thickness: 1.0
  • Lead Pitch: 0.5

Parts & Purchasing

Part Number Pkg Code RoHS Min Temp Max Temp Status Buy Now Order Samples
ST16C2550CJ44-F PLCC44 0 70 Active
ST16C2550CJ44TR-F PLCC44 0 70 Active
ST16C2550CP40 PDIP40 0 70 OBS
ST16C2550CP40-F PDIP40 0 70 OBS
ST16C2550CQ48-F TQFP48 0 70 Active
ST16C2550CQ48TR-F TQFP48 0 70 Active
ST16C2550IJ44-F PLCC44 -40 85 Active
ST16C2550IJ44TR-F PLCC44 -40 85 Active
ST16C2550IP40 PDIP40 -40 85 OBS
ST16C2550IQ48-F TQFP48 -40 85 Active
ST16C2550IQ48TR-F TQFP48 -40 85 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.
Distribution Date Description File
08/17/2016 Qualification of ANST as an alternate manufacturing site. PCN 16-0417-02 ANST-1033.pdf
11/05/2015 Updated information subsequent to original published PCN 13-0834-03 on 04/02/2014. ASE Malaysia as alternate assembly site Addition of qualified alternate assembly site of 28, 44, 68L PLCC packaged products. PCN 13-0834-03A PLCC 28-44-1033.pdf
04/02/2014 Qualification of ASE Malaysia for assembly of 28, 44, 68L PLCC packaged products. Alternate assembly site. PCN_13-0834-03-1033.pdf
12/05/2013 Addition of an alternate qualified assembly site, ASE Chung-Li (Taiwan) for assembly using copper or gold wire bonding. Material change and alternate assembly site. PCN_13-0521-02-1033.pdf
10/03/2013 Product Discontinuation Notification Discontinued. PDN_13-1003-01-1033.pdf
10/17/2012 Exar has qualified Millennium Microtech/Thailand as an alternate assembly supplier for 28, 44 and 68 lead PLCC packages in addition to the existing supplier, Unisem/Indonesia. Capacity enhancement PCN_12-0824-01-1033.pdf
08/10/2011 Material change and a new assembly & test supplier (ASE, Kunshan). Business consolidation. PCN_11-0724-01-1033.pdf
04/11/2011 Product Discontinuation Notice In support of “green” initiatives, the listed leaded part numbers will be discontinued by Exar. PDN_11-0411-01-1033.pdf
09/09/2009 Utilize an existing qualified alternate assembly and test supplier. Business consolidation. PCN_090903-01-1033.pdf