Service manual

PC- l600
4·3. Sub CPU opera ti on
(Interf acing with th e main CPU)
TC8516F (UART)
DO
07-
(dal a bus)
DSTB
IIDSV
ACK
DAIAS
uxh-r
IORP
(from S C1852)
roo •• ·······1
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Buffer
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r
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LU5181JP !wbCPU)
KI
ZIO
z'
RI B-ROO
R
33 - R20
Co nlained in the LR38041 gallluay
Fig. 4
S ig nals interfaced with the main CPU are KI, Z10, Z9,
A 13-AOO, and A33- R20.
Rt3 - R OO =::)< Comm.1Id Xc ____ ___ _
kt I \3" . r;;;:l
'"
"
The following shows signal timings.
R .ody
y
Sand c;ommend
Send command s trobe
ACK n tCa ilild
N
-- -- - --- ...,
R • ..,
- 6 -
<D Before the Z- BO CPU sends a command to the sub
CPU , the sub CPU is asked if it is ready to receive the
command. If it is not, the Z-BO waits until the sub
CPU becomes ready.
The Z-80 assumes the sub
CPU to be ready if the
BUSY input of the UART is high.
® Next, 8-bit command data are sent to the sub CPU .
The
Z-BO sends the data on the DA TA1-DATAB port
of the UART, w
hi ch are received by the sub CPU
through A13-ROO. Un l ess ACK is returned wit hi n one
second, the Z-
BO proceeds to the next proce ssi ng.
® The Z.aO sends a pulse signal on DSTB of the UART in
order ,
to in fo rm the sub CPU a command request,
which the
sub CPU receilles of through the Klline .
With the Kt line of the sub CPU high. an interrupt
is sent to the sub CPU, and the command is processed
in the interrupt se rvice routine.
(!) One of the fo ll owing requests may be made depending
on the command issued fr
om the Z·80.
(i) A request far return data
(ii) A request not to return data
The sub CPU then interprets
the abolle to proceed to
the next step.
(i) A pu lse signal is sent on Z9 after sending the
return data on R33- R20,
to indicate completion
of the command executio
n.
(i j) A pulse signal is sent on Z9 to indicate receiPt
of
the command.
In either case, the Z-80 waits for a high pul
se signal
state on Z9.
The high state recei
ve d on Z9 is then input to the
ACK line of the UART and latched in ternall y, The
Z-80 checks the latch
if it is okay.
® When the Z-80 accesses 33H of li D to request the
return data, it forces IORP
to low so that the LR38041
gate array internal buffer
is opened to send the retu rn
data (R33- R20) on the Z.aO bus D7 - DO.