ZBOQT
Table
3-1.
280 Signals (cont)
SIGNAL NAME
DESCRIPTION
MREQ Line
W—Fl
Line
RFSH Line
HALT Line
AIT Line
WT
and
N
Lines
3
The
MREQ
output
identifies a memory
access
operation
in
progress. The 280 places
MREQ
at
logic
low
during any memory
access
operation.
In
addition,
MREQ is
placed
in
a high impedance state
during
DMA
operations. See
BUSRQ.
The
IOFlQ
output identifies any l/O operation
in
progress. When
lORQ is low,
address
lines A0
-
A15
contain a
valid
l/O
port
address. The
IORQ line is
also
used
in
conjunction
with
the
W
line
as an interrupt
acknowledge. When the 280 acknowledges an
inter-
rupt, both lines
are
driven low.
low.
The
725
output
is
pulled
low
to
indicatethat
the 280
is
ready to read
data
via
the data lines from either
memory or an l/O device, as identified
by
the
MREQ
or
IORQ line.
In
addition,
Fl_D
is
placed
in
a high
impedance state during
DMA'
operations. See
BUSRQ.
The
W
output
is
pulled
low
to indicate that the 280
is
ready to write data
via
the data lines to either
memory or an l/O device,
asflantified
by
the
MREQ
or
IORQ line. ln
addition,
WR is
placed
in
a
high
impedance state during
DMA
operations. See
BUSRQ.
The
RFSH
output
is
a control signal which may be
used
in
conjunction with the
MREQ line
to refresh
dynamic memories. When
RFSH is
pulled
low
the
MREQ
signal and address lines
A0
-
A7
may
be used
to
refresh dynamic memories.
The
HALT
output
is
pulled
low
following the
execution
of
a halt instruction. During the halt state,
the 280 continuously executes a
NOP
instruction
in
order to maintain memory refresh
activity.
The
WAlT line is
an input which, when placed at a
logic
low level,
causes the
Z80
to enter a wait state.
During the wait state,
the
280 inserts clock pulses to
extend
the
cycle time as required
by
the external
logic selecting the wait state.
The
W
line
is an
input which permits external
interrupt of
the
280 as long as interrupts are not
disabled and the
BUSRQ line is
not at a logic
low.
The
W
line
is
a non-maskable interrupt input
which cannot be disabled.
Содержание 9000A-Z80QT
Страница 6: ......
Страница 14: ......
Страница 18: ...ZBOQT Figure 2 3 Connection 0 Interface Pod to UUT...
Страница 72: ......
Страница 76: ...Z8OQT MP10 H 2 9000A Z8OQT 5071 Figure 6 1 9000A 2800T Intertace Pod Final Assembly...
Страница 84: ...Z8OQT E 3 mwmdwwwwmi o a u n v u 2 as MLVLSI IQ 23333329...
Страница 85: ...ZBOQT QLVLSNXVI 9 Figure 7 1 A11 Processor PCB Assembly...
Страница 86: ...ZBOQT H H u Chum 55 ixu m3m V V v 0 A0 m v mmmcaa 5 5 taxman th XEH 35me 9 02 hww m4mm Nu W tho mu m uw m 7 4...
Страница 88: ...2800T 7 6 m V L LOl D INPUTS PAL U27 LOGIC Flgure 1 1 A11 Processor PCB Assembly cont OUTPUTS 15...
Страница 89: ...ZBOQT DEVICE 6ND PINS 14 Figure 7 1 A11 Processor PCB Assembly cont 7 7...
Страница 90: ...Z8OQT LA SELF HOLD LO BUSAK 7 8 C 2 5 5v 22A if 22L l clz Em 0531 00 463 EEF tzaF L _____________ _J...
Страница 92: ......
Страница 108: ......