Sharp MZ-5600 Service Manual page 18

Pin used for minimum mode.
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bel!oTable 11 .. b
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k!inNo.
Pin name
Function
1
,.
28
M/la
Deta tra nsfer
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1
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111
",':'29
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1
24
25
27
26
31
( ' I
30
control output
WR
Wirte control
output
1NTA
Interrupt ac-
knowledge output
ALE
Address latch
enable output
DT/R Deta send/receive
control output
DEN
Data enable
output
HOLD Hold request
input
HLDA Hold acknowl·
edge output
Pins used for maximum mode.
Table 11·c
Pin No. Pin name Function
26
SOS251
Status output
1
28
30,31 RQ/GTO Request/grant
RQ/GT1 input/output
29 LOCK Lock request
output
24,25 QS1, QSO
Queue status
output
IN/OUT
OUT
OUT
OUT
OUT
OUT
OUT
IN
OUT
IN/OUT
OUT
IN/OUT
OUT
OUT
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M Z-5600
Description
Indicates whether the CPU is accessing the memory or an I/O device.
Indicates the timing of write operations to an external memory or I/O device.
Used as a strobe to read interrupt vectors on the data bus during the interrupt
acknowledge cycle. Also indicates an interrupt acknowledge to the device in
request for interrupt.
Strobe used to load address information (which is output from the CPU on
time-division scheme) into external latches.
Indicates the direction of data transfer to an external data bus buffer.
Enables the external data bus buffer.
When receiving a Hold request, the CPU relinquishes bus access authority and
enters the Hold state immediately after completing the current machine cycle.
Indicates that the CPU acknowledged the Hold request and relinguished bus
access authority, to the device in request.
Description
S2 S1
SO
0 0 0
. Interrupt acknowledged.
0 0 1 Read I/O port.
0 1 0 Write I/O port.
0 1 1 Hold
1 0 0 Fetch instruction.
1 0 1 Read memory.
1 1 0
Write memory.
1 1 1
Passive cycle.
Used to receive Hold request and output Hold acknowledge when a device other
than the CPU wants to use the local bus. The RQfGTO pin has a higher priority
over the RQfGT1 pin.
Used to inhibit other system bus masters accessing the system bus when the
CPU wants to use the system bus. --
Indicates operations performed at the instruction queue:
QS1 QSO
0 0 No operation.
0 1 Fetches the first byte (OP code) of an instruction.
1 0
Clears the contents of the queue.
1 1
Fetches the second and subsequent bytes of the instruc,
tion.
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