8.4.6 Block Transfer Mode
In block transfer mode the A and B channels are combined. One block of a specified size is
transferred per request. A designated number of block transfers are executed. Addresses are
specified in MARA and MARB. The block area address can be either held fixed or cycled.
Table 8-10 indicates the register functions in block transfer mode.
Table 8-10 Register Functions in Block Transfer Mode
Register
Function
Initial Setting
Operation
Source address
Source address
Incremented or
register
decremented once per
transfer, or held fixed
Destination Destination Incremented
or
address register
address
decremented once per
transfer, or held fixed
Block size counter Block size
Decremented once per
transfer until H'00 is
reached, then reloaded
from ETCRAL
Initial block size
Block size
Held fixed
Block transfer
Number of block
Decremented once per
counter
transfers
block transfer until H'0000
is reached and the
transfer ends
Legend
MARA:
Memory address register A
MARB:
Memory address register B
ETCRA: Execute transfer count register A
ETCRB: Execute transfer count register B
The source and destination addresses are both 24-bit addresses. MARA specifies the source
address. MARB specifies the destination address. MARA and MARB can be independently
incremented, decremented, or held fixed as data is transferred. One of these registers operates as a
block area register: even if it is incremented or decremented, it is restored to its initial value at the
end of each block transfer. The TMS bit in DTCRB selects whether the block area is the source or
destination.
23
0
MARA
7
0
ETCRAH
7
0
ETCRAL
23
0
MARB
15
0
ETCRB
218
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