Main Menu 422/485 4 Port ISA

Blastronix delivers high performance RS 422/485 4 port ISA media card

RS 422/485 4-Port ISA Card

Model Description Price
422/4S-ISA 422/485 4 Serial Port 199.00

Quick Look

16C550 UARTS standard on all cards

Multiple 485 enabling options

IRQs 2/9 3, 4, 5, 6, 7, 10, 11, 12, 14, 15

Individual port addressing 0 - 3FF hex

Baud rates to 115.2K bits per second

DTE / DCE selectable RS232 ports

Interrupt status register with sequencer 

Digiboard, Hostess, AST, emulation

To order:
Call us: (209) 795-0738
Fax us: (209) 795-0646
We except VISA, MasterCard, American Express, Discover, COD, & Net 30 accounts upon approval of credit.
Warranty: In most cases, our reliable products carry a lifetime warranty. See below for details.


Blastronix now offers an extensive line of low cost, high performance RS422/485 cards. All cards come with 16C552 UART's which feature 16 byte transmit and receive buffers to help guard against loss of data in your system. The 16C552 is a dual port version of the popular 16C550 UART. All cards may be addressed as COM1 - COM4 or any other I/O address you choose up to 3FF hex. Because each port's address may be defined individually, you don't have to worry about address conflicts as you do with cards which use 32 and 64 byte blocks for addressing. These cards operate at speeds of up to 115.2 bits per second and transmit distances of up to 5000 feet. They offer numerous features which you may take advantage of or you may simply choose to use the card in it's simplest mode as a standard 422 or 485 card.

Enabling Options

A number of options are available for enabling the 422/485 interface. The driver and receivers may be enabled at all times as in a typical 422 environment. Additionally, the driver can be enabled and the receiver disabled with RTS. Drivers and receivers may be individually controlled by setting and resetting bits 0 and 1by writing to the base address + 7 register. The card also features an Auto Enable option which requires no software to control the drivers and receivers. Simply send the data and the driver is turned on and the receiver is turned off automatically.


Our interrupt sharing allows multiple ports on a single card, as well as multiple cards in a single system, to all use the same interrupt. Interrupts between two 4 port cards may be daisy chained to allow the card to look like a single 8 port unit to the software. Eleven interrupt choices are available for each port. These include IRQ's 3, 4, 5, 6, 7, 9, 10, 11, 12, 14, and 15. The interrupt status register may be located at any address and when used with interrupt sharing it will supply you with a pointer to indicate which port has an interrupt pending. This feature allows you to find out which of up to 8 ports has a pending interrupt with only a single read operation thereby reducing interrupt overhead significantly. The onboard interrupt sequencer further reduces interrupt overhead by providing only one pending interrupt at a time. After the status register is read the next pending interrupt is loaded into the status register. These units are compatible with the protocol used by Digiboard.

RS422/485 Interfacing

These cards support both RS422 and RS485 with a jumper option for both 2 or 4 wire operation. Drivers and receivers may be always enabled, or enabled with RTS. With Auto Enable mode selected all you need to do is send the data and the driver is automatically enabled and the receiver disabled. In auto enable mode software overhead is minimized so you do not need to turn on or off the drivers and receivers. Drivers are disabled within a few microseconds of transmission of the stop bit. Drivers and receivers may also be independently controlled with data bits 0 and 1 by writing to the base address +7 for the port. (Metrabyte COM485 protocol compatible). RTS and CTS flow control is supported as well. Convenient on board jumpers allow for 220 ohm termination as needed.


These cards are compatible with all application software that communicate with a standard serial port using an 8250, 16C450, or 16C550 type UART. Also compatible with, OS/2, Windows, Windows NT, UNIX, and XENIX. (Windows NT and UNIX have the interrupt status register support built in as part of the operating system)


Blastronix products comply with certifications such as RoHs, Weee, and SMPTE. Please inquire for details.

  • Part Number: ................................9220008
  • Blastronix Model:............................422/4S-ISA
  • Operating Systems..........................Win98, ME, NT,Win2k, XP, VISTA
  • Businterface:.................................ISA
  • Serial Ports:..................................4 ports
  • Transmission speed:........................ Up to 115.2K bits per second
  • Max Data Distance:..........................4000 feet/interface dependent
  • Operating Temperature:....................0-70 degrees C
  • Storage Temperatur:.......................-50-+105 degrees C
  • Humidity Range:.............................10-90% Relative Humidity


Because our products are so reliable, Blastronix confidently offers warranties on all our products. In most cases, our serial boards are warranted against manufacturing and production defects in function and workmanship for life. In the case of product malfunction due to damage by a third-party (including acts of God) and not due to manufacturing workmanship is not covered under warranty. Please inquire for more details.


Model Description Price
422/4S-ISA 422/485 4 Serial Port 199.00

To order:
Call us: (209) 795-0738
Fax us: (209) 795-0646
We except VISA, MasterCard, American Express, Discover, COD, & Net 30 accounts upon approval of credit.