Zenith Z-100 Series, Техническое руководство

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Page 10.5
GENERAL INFORMATION
Processor Swapping
The Computer contains two processors, with selection cir-
cuitry to enable the desired processor. Processor swap occurs
when the presently selected processor writes to bit 7 (MSB)
of the processor swap port (PSP). A 1 selects the 8088 and
a 0 selects the 8085. The processor swap port is port FE.
When a processor swap occurs, the newly selected processor
can restart from where it left off, or an interrupt can keep
it from starting. Interrupt generation is enabled by writing a
1 to bit 1 of the PSP.
If interrupts are not masked, the currently selected processor
is signalled when an interrupt is requested. If the MASK mode
is selected, no interrupts will get through to the 8085 and
the 8088 will service all interrupts. In the MASK mode, the
8088 is selected whenever an interrupt occurs. MASK is bit
0 (LSB) of the PSP. A 1 activates this function.
Bit Defi n i tion
0 0
= Both processors receive interrupts
1
= Force a processor swap to 8088 if 8085
active
0 = R e s ume execution from previous address
1
=
Force an interrupt as newly selected pro-
cessor becomes active
7 0
= Select 8085 processor
1 = S e l ect 8088 processor