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Home >> Products >> I/O Connectivity ICs >> PCIe Bridge >> MCS9904

 MCS9904 -- PCIe to Quad Serial Controller

MCS9904 is a single lane multifunction PCI express to I/O controller. MCS9904 supports four serial ports and eight GPIO's. MCS9904 also provides an option for peripheral expansion through proprietary Cascade interface. The generic cascade interface allows interconnecting with other ASIC's like MCS9900 to expand the peripheral ports.

The serial ports are compatible with RS232, RS422 & RS485 standards and supports throughput from 50bps to 16Mbps. All the GPIO pins are programmable and can be used as Input or Output. An I2C interface is provided to configure MCS9904 device options through an external EEPROM.


  • PCI Express
    • Single-lane (X1) PCI Express End-point Controller with integrated PHY
    • Compliant with PCI Express Base Specification, Revision 1.1
    • Compliant with PCI Express card specifications
    • Supports four PCI Express functions
    • Supports auto completion of configuration requests
    • Supports built in flow control
    • Supports Message TLP (Error) generation
    • Supports integrated time out handling of Non-posted request
    • Supports both legacy and MSI Interrupt
    • Supports PCIe Power Management
  • Serial Port
    • Four 16C450 / 550 / Extended 550 / 650 / Enhanced Mode compatible UARTs
    • Supports RS232, RS422 & RS485 modes
    • Bi-directional speeds from 50 bps to 16 Mbps per port
    • Full Serial Modem Control
    • Supports Hardware, Software Flow Control
    • Supports 5, 6, 7, 8 bit Serial format
    • Supports Even, Odd, None, Space and Mark parity
    • Supports Custom baud rate by programming internal PLL or external clock
    • Supports On Chip 256 Byte depth FIFOs in Transmit, Receive path of each Serial Port
    • Supports remote wakeup and power management features
    • Serial Port transceiver shutdown support
    • Supports Slow IrDA mode (up to 115200bps) on all Serial Ports
  • Cascade : MCS9904 supports a 13-Pin proprietary interface to connect to other ASIX devices for IO expansion. Through this interface, MCS9904 can be used as Cascade Secondary device and can be connected to Cascade Primary capable ASIX Devices like MCS9900. Eg. MCS9904 can be connected to MCS9900, for following product configurations
    • PCIe to 8 Serial Ports
    • PCIe to 6 Serial Ports and one Parallel port
  • General Device Features
    • I²C interface for EEPROM
    • EEPROM read / write through PCIe Interface
    • 8 bi-directional multi-function GPIO lines
    • On chip oscillator
    • Power supply : 1.2V, 3.3V
    • Package : 128-Pin LQFP, RoHS
    • Operating Temperature : 0 to +70°C
Target Applications:
  • Serial Attached Devices
  • Serial Networking / Monitoring Equipment
  • Data Acquisition System
  • POS Terminal & Industrial PC
  • Add-On I/O Cards - Serial
  • Embedded systems - For I/O expansion

 Block Diagram


 Selection Guide


Technical Documentation

 Product Brief, Product Introduction and Datasheet

MCS9904 Product Brief261.9 KB2012-05-10
MCS9904 Datasheet 1.8 MBv2.202020-05-08
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MCS9904 Reliability Report 193 KB2011-12-07
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MCS9904 RoHS Report   
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Hardware Design Documentation

 Reference Schematics

MCS9904 PCIe 4 Serial Reference Schematic 328.4 KBv2.002015-03-16
MCS9904 PCIe Minicard 4 Serial Reference Schematic 245.3 KBv2.002015-03-23

 Bill of Materials, Application Notes and Layout Guides

MCS9904 PCB Layout Guide 235.9 KBv1.002011-09-28
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 PCB Layout, Gerber and IBIS Model

MCS9904 IBIS Model 319.8 KB2015-04-08
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Driver TypeRevision Release DateDescriptionFile Size
Linux kernel 4.x/3.x/2.6.x Driver V3.1.02016-05-11 For all Android systems, Linux kernel 2.6.15 and later25.1 KB
Windows 10/8.x 32-bit Driver V3.18.1.02016-08-01 For 32-bit x86 CPU platform, HLK/WHCK certified434.6 KB
Windows 10/8.x 64-bit Driver V3.18.1.02016-08-01 For 64-bit x86 CPU platform, HLK/WHCK certified512.1 KB
Windows 7/Vista/XP 32-bit Driver V3.12.1.02016-08-01 For 32-bit x86 CPU platform, WHCK certified407.9 KB
Windows 7/Vista/XP 64-bit Driver V3.12.1.02016-08-01 For 64-bit x86 CPU platform, WHCK certified492.4 KB
Windows CE 6.0 Driver v1.0.0.12009-06-05 For CEPC x86 platform1.5 MB
Windows CE 5.0 / Mobile 5 / Mobile 6 Driver v1.0.0.12009-06-05 For CEPC x86 platform952.4 KB
DOS Configuration Tool v1.0.0.32011-02-24 For MS-DOS Legacy I/O Ports Configuration381.9 KB


click here for more MCS9904 FAQs....
Q0001: Where can I obtain the latest MCS9900/MCS9901/MCS9904/MCS9922 datasheet, reference schematic and other hardware design archives?
A0001: Please register MyASIX membership ( and then download the latest MCS9900/MCS9901/MCS9904/MCS9922 datasheet, reference schematic, PCB layout guide, etc. from ASIX I/O Connectivity Product web pages ( directly.

Q0002: Can ASIX help me to review my own MCS99xx schematic and PCB layout?
A0002: Yes, please deliver your own MCS99xx schematic and PCB layout files to ASIX's Support ( for further review before making your own MCS99xx PCB board.

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