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Seattle Computer Products -- SCP 301   8086 Support Board

SCP 8086 support board was very much a part of a functional SCP 8086 system. Much of the early 16bit DOS was built around this board.

SCP Support Board

The board had room for an optional onboard ROM monitor. This was usually some form of the SCP supplied 8086 monitor. The ROM could be either an Intel-type 2716 or 2732. It resided near the end or memory, as determined by either the usual 16 address lines, or by IEEE 696, 20 address  lines (extended addressing).  The board could drive the  PHANTOM line to  allow a memory board to overlap with it on the bus. This could be disabled with an software output command.
A serial communication port,  including RS-232  drivers with full handshaking was included.  A software controlled baud rate generator allows almost any conceivable data rate to be used. 

There was a parallel input port,  latched and with full handshaking.  This port could provide +5V or +8V to power an external device (such as a keyboard).   There also was a parallel output port. Again full handshaking was provided with an output that may be statically latched and driving at all times or configured for 3-state output which allowed bidirectional operation. 

There was an onboard vectored interrupt controller. This provided  15 levels of vectored interrupts, expandable to 64 through 'slave' controllers on other cards (such as the SCP Multiport Serial card).

The board had two general-purpose timer/counters. Each was 16 bits wide. One could be combined with the time-of-day clock to count days.

There was also on board a time-of-of day clock. Time of day was kept in 24-hour format to 0.01 second. Power to run the clock may be provided from an external source, such as a battery, to keep the clock running when the computer power was off. If time of day was not needed, the clock could be used as two general-purpose 16-bit timers.

Finally like the TDL SMB board there was an "IOBYTE" type "sense switch" input port. This allowed the reading the setting of an 8-position DIP switch for the purpose of setting software options or configuration information.

Each of the above functions were controlled by a block of 16 I/O ports. The upper 4 bits of the 8-bit I/O address are compared with a switch setting to enable the board as a whole; the lower 4 bits select the particular function on the board.
The detailed manual (with schematic) for this board may be obtained here
A later version of the manual (without schematic) can be obtained here.


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This page was last modified on 10/25/2013