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3-3-10. External Slot Access
The CPU accesses devices external to the MPU-7 board in the
following four cases:
1) When it accesses boards installed in the expansion I/O
slots
2) When it accesses the display controller circuit board
(DSC-008)
->
EXIO access
3) When it accesses an optional sound board
->
special access
4) When it fetches an interrupt vector in response to a
request issued by LH8530A on the NWB-231A board installed
in an expansion I/O slot
->
VECT access.
The above can be classified into three type sequences,
1 and
2 being
basically identical.
3-3-10-1. EXIO access
EXIO access is used by the CPU to access a board installed in
one of the expansion I/O slots or the DSC-007 dedicated
black-and-white display controller.
The DSACK signal cannot
be generated automatically by MPU-7 internally.
It is input
via an external connector.
A bus error is generated if an
attempt is made to access a non-existent address.
A flowchart
of this process is given below.
a) Normal operation
3-22
NWS-1510/1530/1580
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