Specifications
4 - 19
If you plan to use SCSI interface in non-SCSI applications, you will probably require a copy of the
AIC-6250 SCSI Chip technical manual referred to previously in this chapter.
4.7 BYTE-WIDE MEMORY SOCKETS
The two 28-pin byte-wide memory sockets at U32 and U33 support a variety of 28-pin JEDEC
pinout memory devices, including EPROM, static RAM, EEPROM, page-addressed EPROM, and
nonvolatile RAM (NOVRAM) cartridges. Chapter 2 includes a table indicating the types and
capacities of the memory devices each socket will hold. Ampro's solid state disk (SSD) drive
support within the ROM-BIOS and optional SSD Support Software treat these sockets as up to
two DOS disk devices, containing as much as 1 megabyte of EPROM SSD storage (both sockets
combined).
The byte-wide sockets are accessed as 8-bit devices, each within a separate memory area. Note
that the address space of each socket is fixed at 32K bytes, regardless of the type of device being
used. This means that when smaller devices or page-addressed EPROM's are used, these devices
are "mirrored" (i.e. appear at multiple addresses) within the 32K byte socket window.
The byte-wide sockets can be disabled by the ROM-BIOS at powerup and boot time via options
stored in the board's configuration EEPROM (initialized using the SETUP utility). Additionally,
the sockets can be enabled or disabled under software control, using a special ROM-BIOS call
provided for this purpose. When a byte-wide socket is disabled, its address space is available on
the expansion bus; but when a socket is enabled, its address space is not available on the bus.
The sockets are accessed with four wait states. The required speed of devices used in these
locations is 300 nS (or faster), on both 12 MHz and 16 MHz boards.
The following example shows a simple assembly language routine that controls the byte-wide
memory sockets:
MOV AH,0CDH ; AMPRO function call
MOV AL,nn ; Use "03" for U32 or "04" for U33
MOV BX,nn ; Use "00" to turn OFF or "01" to turn ON
INT 13H