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Dedkated to enhancing the performance of multi-user S-100 >ystems, the MPX MULTIPLEXER CHANNEL is a
special purpose processor boan:l that relieves the system's main CPU from ha,·ing to handle repetitive l!O operation<.
Rather than having to interrupt the CPU every time a terminal is ready to receive a b)1C of data. and then wai1ing
while the CPU executes several hundred bytes of code, the MPX can transfer the same byte of data almost instantly
by '';!ealmg'' only two or three bus cydes. This eliminates 98 to 99"70 oft he CPU time norm ail)' wasted on handhng
this kind of overhead, resulting in increa<;ed speed and throughput that dramaticall)' improves the performance of
any S-100 S)'Stem in multi-user applications. Virtually a computer in itself (not just a stripped down b"ard), the
MPX includes the following impo11ant features:
• 6 MHz 8085AH-1 microprocessor.
• 2K of on-board 2716 EPROM, and 16K of on-board RAM. allows the 8085 to run concurrently with
the main system CPU.
• EPROM socket can also accept 2732 or 2764 EPROMs.
• On-board interrupt controller interrupt' the MPX when a de,·ice on the bus requires service.
• The MPX ma;· call the CPU by generating an interrupt.
• Full IEEE 6%/S-100 temporary master interface allows the 8085 dire<:! bu' access by interlca'1ng" ith
normal buo cycles r·cycle stealing")_
• DMA (Direct Memory Access) cycle' may address the full 24 bit (16 megabyte) extended address range.
• DPA (Direct Pot1 Access) cycles allow emulation ofZ80 110 modes b;· permitting software control of all
-;ixteen add res• lines.
• Fully compatible with any existing interfaces.
• Attention port all(}ws the CPU t(} call the MPX.
• The MPX can respond to a bus interrupt acknowledge cycle: therefore, no other mtcrrupt controller i>
required.
• For maximum u>er flexibility (and to allow for no.-el or special-purpose applications). the MPX may load
software into its own RAM dirixtl}' from the bu<;.
Thanks to the above hardware capabilities. the MPX efficient!~- - and transparently - automate~ the tran>fer of
data between user programs and peripheral interfaces. However, in additi(}n to performing data tran;fer, for 'crial
!/O ports, the MPX may serve as a resource scheduler for high speed devices by sending commands to. and
processing completion interrupts from high speed DMA disk controllers. f(}r extra flexibility, the MPX may load
software from the bus into it> integral on-board RAM and then execute that code, allowing the function oft he MPX
to change d}·namically in response to changes in the system requirements.
The MPX ha ne"' piece of hard" are that makes troly efficient mult1programming an affordable realil)·.
(GmpuPrC:)
"&IJl1lll1IJ1 COMP..NV • O"KU.ND "IRPORT. CA 9'/;H
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