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Dual Systems --  SIO4  Serial I/O Board

The SI04-DMA was an intelligent, high performance, four-port serial input/output board. It conformed to the IEEE-696/ S-100 specification but is also designed to work with older S-100 systems.

Dual Systems 4Port Serial Card

The board was intended to be used with asynchronous terminals or printers in multi-user systems and had the necessary features to work with modems. A limited synchronous mode capability added flexibility.

All input data to the SI04-DMA passed through a 256-byte FIFO buffer, removing the requirement for a fast response time from the operating system and avoiding the possibility of "lost" characters. On output, the SI04-DMA reads characters directly from the S-100 machine's memory via DMA and transfers them to the serial port. This reduced the operating systems over­head for output operations several hundred times. The board was capable of a full 24-bit address range and incremented over any address boundary.

Baud rate was independently selectable on each channel by program. Sixteen of the most popular speeds were provided.

The SI04-DMA was the first S-100 serial interface board designed specifically to reduce operating system overhead in multi-user systems. The tasks normally performed by the operating system to handle serial input and output are assisted by intelligence built into the onboard microcomputer (8085A) assisted S104.

Bus Compatibility: The SIO4-DMA was compatible with the IEEE 696/ S-100 specifications as defined in January 1982 and was suitable for systems with up to 8MHz clocks. The SI04-DMA was also intended lo be compatible with many older S-100 computers.

IEEE 696/S-100 Compliance: M24, VI, TM, F8, W1-16. Number of wait states depends on S-100 dock rate and state of SI04-DMA when accessed.

Address Selection: I/O address selected by DIP switch. Eight bits of VO address are decoded.
Operating Power: The maximum power consumption is: +8 Volts® 1.3 Amps +16 Volts® 0.1 Amps -16 Volts ©0.1 Amps

RS-232 Compliance: All RS-232 drivers and receivers conform to the RS-232 specification. The SI04-DMA can simulate either a modem (DCE) or terminal (DTE) for connection to a terminal or modem respectively.

Synchronous Mode: In the synchronous mode the external clock signal determines receive baud rate. A transmit clock is provided by the SI04-DMA at the selected baud rate. Baud Rates:
Baud rates are available:  45.5.....9600.....3840.

I cannot locate a better image for this very useful board. Nor can I locate a manual. 
If you would like to submit one or both please let me know.

There is a great write-up on this board in the March 1984 Microsystems Journal (Vol 5, p103).


Other Dual Systems S-100 Boards
68000 CPU    256K RAM    Clock Board   CMEM-RAM    Digital-to-Analog    Analog-to Digital    4SIO    EPROM


This page was last modified on 10/25/2013