MEMORY PLUS Manual By Lee Davison and Hans Otten Back to The Computerist

					EPROM Memory
	
	The Erasable Programmable Read-Only Memory (EPROM) used with MEMORY PLUS is
	an ultraviolet erasable and electrically programmable 2716 type ROM.  This is
	a fairly new memory chip.  The version used in MEMORY PLUS is made by INTEL.
	It is not compatible with the 2716 made by some other manufacturers such as
	Texas Instruments.  It may be second sourced by other manufacturers, but be
	certain that any EPROM you purchase is at least INTEL 2716 compatible.  Each
	2716 chip contains 16,384 bits of memory.  The addressing of the chip is such
	that data is accessed eight bits at a time.  The organization is 2048 bytes of
	eight bits each.  A single 2716 provides 2K bytes of memory.  The MEMORY PLUS
	board has provision for up to four 2716 chips providing for a maximum of 8K
	bytes of EPROM.

	The 2716 chips required for MEMORY PLUS are INTEL 2716 or equivalent (Texas
	Instrument 2516 but NOT T. I. 2716).  This chip has the following basic
	parameters:

		SPEED:	450 nanosecond access time

		POWER:	105 milliamp worst case current, and
			single +5 volt required

	The MEMORY PLUS EPROM is organized into a single contiguous 8K block of memory.
	The location of the EPROM in the MICRO addressing space is defined by a switch
	which may be set to start at any 8K boundary (2K hex boundary).  See the chart of
	switch positions on the preceding page.  The position is determined by the flat
	section of the switch.

	(KIM 1 ONLY):   If; and only if, the "EK" address is used, then the jumper "J1"
	(located on the top side of component U4) must be changed.  The existing jumper
	etched on the board must be cut and a wire run from the hole nearest the "J"
	to the hole nearest the  "1". This will cause interrupts to be serviced by the
	FFFx vectors instead of the 1FFx KIM-1 vectors.

	The EPROM sockets are addressed such that the socket nearest the edge of the
	board has the lowest address.  The exact layout of the individual EPROM chips
	may be found in a diagram in the section on "MEMORY PLUS Testing and Field Repair"


				VIA Address Selection

	There are several ways to address the MEMORY PLUS VIA chip.  There is circuitry
	on the board which will normally address the VIA starting at 6200.  This is
	accomplished by combining the 6000 signal generated by the 74LS138 at U4, pin 12,
	with address lines A8 and A9 in the 74LS32 at U6.  If this address is in con-
	flict with something in your system, it may be changed in several ways.  The
	easiest change is to use any other available (unused) decode signal from the
	74LS138 at U4.  Simply unsolder the existing wire from pin 12 and attach it to
	the new pin.  In this way you can have the VIA addressed as 2200, 4200, 6200
	(which is the way the MEMORY PLUS board is shipped), 8200, A200, or C200.  If
	these other addresses do not solve your problem, then you can provide from an
	external source a signal at pin L of the Application Connector in place of the
	signal from U4 discussed above.  The U4 wire must be disconnected.  The VIA
	address will be the value of the external signal to pin L, plus 0200.  For
	example, using the KS signal (1400) from the KIM-1 or SYM-1 will cause the VIA
	addresses to start at 1600 (1400 + 0200   1600).  IMPORTANT NOTE:  If you do
	change the VIA address, then locations 0006 and 0007 in the EPROM Programming
	Program must be changed before using it.