Z8S18020VSG Datasheet, PDF (57/71 Pages) Zilog, Inc. – Two Chain-Linked DMA Channels

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The DMA I/O Address Register specifies the I/O device for
channel 1 transfers. This address may be a destination or
source I/O device. +#4. and +#4* each contain 8 address
bits. The most significant byte identifies the Request Hand-
shake signal and controls the Alternating Channel feature.
&/# +1 #FFTGUU 4GIKUVGT %JCPPGN  .QY
/PGOQPKE +#4.
#FFTGUU $*
(KIWTG  &/# +1 #FFTGUU 4GIKUVGT %JCPPGN  .QY
&/# +1 #FFTGUU 4GIKUVGT %JCPPGN  *KIJ
/PGOQPKE +#4*
#FFTGUU %*
(KIWTG  &/# +1 #FFTGUU 4GIKUVGT %JCPPGN  *KIJ
&/# +1 #FFTGUU 4GIKUVGT %JCPPGN  $
/PGOQPKE +#4$
#FFTGUU &*
#NV' The #NV' bit should be set only when both DMA
channels are programmed for the same I/O source or I/O
destination. In this case, a channel end condition (byte count
= 0) on channel 0 sets bit 6 (#NV%), which subsequently
enables the channel 1 request and blocks the channel 0
request. Similarly, a channel end condition on channel 1
clears bit 6 (#NV%), which then enables the channel 0 request
and blocks the channel 1 request. For external requests, the
request from the device must be routed or connected to both
the &4'3 and &4'3 pins.
#NV% If bit (#NV') is 0, the #NV% bit has no effect. When bit
7 (#NV') is 1 and the #NV% bit is 0, the request signal selected
by bits   is not presented to channel 1; however, the chan-
nel 0 request operates normally. When #NV' is 1 and #NV%
is 1, the request selected by 5#4  or &#4  is
not presented to channel 0; however, the channel 1 request
operates normally. The #NV% bit can be written by software
to select which channel should operate first; however, this
operation should be executed only when both channels are
stopped (both &' and &' are ).
4GS5GN If bit &+/ in the &%06. register is 1, indicating
an I/O source, the following bits select which source hand-
shake signal should control the transfer:



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#5%+ 4&4(
#5%+ 4&4(
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$KV        
#NV' #NV%
4GS  5GN
If &+/ is 0, indicating an I/O destination, the following
bits select which destination handshake signal should con-
trol the transfer:
(KIWTG  &/# +1 #FFTGUU 4GIKUVGT %JCPPGN  $



1VJGT
&4'3 RKP
#5%+ 6&4'
#5%+ 6&4'
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