3. Theory of Operation
36
NE2000 compatible) the PROM can be mapped into any 8, 16, 32, or 64 Kbyte
boundary beginning at one of eight software selectable locations between 0C000h and
0D000h.
If a PROM device is installed on the ZT 8995, memory space must be allocated to it. A
register within the LAN interface chip is used to save the address bits that decode both
the PROM socket and the size of the part. Depending on the size of the PROM device
installed, the recommended PROM base address options are D0000h or D8000h.
Interrupts
Interrupts are supported by the ZT 8995. Interrupts can be output on backplane signals
INTRQ*, INTRQ1*, INTRQ2*, INTRQ3*, INTRQ4*, NMIRQ*, and IRQx. They can also
be output on the frontplane connector. The "
Interrupt Diagram
" figure illustrates the
ZT 8995 interrupt structure.
Interrupts are used by the diagnostic program. Interrupts must be properly configured
for the
diagnostic program
to complete all of the on-board tests (a typical selection is
IR9 driven across backplane signal INTRQ*). Note: if IRQ15 is selected, the ZT 8995
interrupt signal must be jumpered to utilize INTRQ3*, NMIRQ*, or one of the frontplane
signals FP1* or FP6*. This signal must be connected to the processor board interrupt
request that matches the interrupt request (IRQ levels) selected using the setup
program
INFOSET or AUTOSET8
. See the "
Interrupt Selection
" table and the jumper
descriptions for
W11-14
for more information.
Note:
The ZT 8995 selection for IR9 on backplane signal INTRQ* is compatible with all
Ziatech factory default jumpered processor boards.
ZT8995
INT0
INT1
INT2
INT3
IR3
IR4
IR5
IR9
IR10
IR11
IR12
IR15
INTRQ1*
INTRQ2*
INTRQ4*
INTRQ*
FP3* (J1, pin #4)
FP5* (J1, pin #6)
FP7* (J1, pin #10)
W11
W12
W13
W14
NMIRQ*
INTRQ3*
FP6* (J1, pin #8)
FP1* (J1, pin #2)
PAL
Interrupt Diagram
Note:
Frontplane numbers may differ from CPU to CPU in their interrupt routing.
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