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Whether a block is to be designated for MARA or for MARB is specified by the BLKDIR bit in
DMACRA.
To specify the number of transfers, if M is the size of one block (where M = 1 to 256) and N
transfers are to be performed (where N = 1 to 65,536), M is set in both ETCRAH and ETCRAL,
and N in ETCRB.
Figure 8-13 illustrates operation in block transfer mode when MARB is designated as a block area.
Address T
A
Address B
A
Legend
Address
T
= L
A
A
Address
T
= L
B
B
Address
B
= L
A
A
Address
B
= L
B
B
Where :
L
= Value set in MARA
A
L
= Value set in MARB
B
N
= Value set in ETCRB
M
= Value set in ETCRAH and ETCRAL
Figure 8-13 Operation in Block Transfer Mode (BLKDIR = 0)
1st block
2nd block
Nth block
SAID
DTSZ
+ SAIDE · (–1)
· (2
DAID
DTSZ
+ DAIDE · (–1)
· (2
Transfer
Consecutive transfer
of M bytes or words
is performed in
response to one
request
· (M·N–1))
· (N–1))
Address T
Block area
Address B
B
B
259
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