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7721 Group User’s Manual
13-28
DMA CONT R OLLE R
13.3 Control
13.3.6 DMA transfer restart after termination
(1)
Restarting the same DMA transfer as the previous one from the beginning
At normal and forced termination, the latches of SARi, DARi, and TCRi maintain their values written
before the transfer start. (Refer to
“Figure 13.3.4-a.”
) Therefore, DMA transfer must be restarted
according to the following procedures:
G
In single or repeat transfer mode
Set the DMAi enable bit to “1.” It is not necessary to re-set the values of SARi, DARi, and TCRi
by software. (Refer to
“Figure 13.3.4-b.”
)
G
In array chain or link array chain transfer mode
Re-set the values of SARi and TCRi.
Set the DMAi enable bit to “1.”
(2)
Restarting transfer of data subsequent to one which has been transferred just before forced
termination
When reading values at the addresses of SARi, DARi, and TCRi after forced termination, the values
of these registers (counters) can be read. These read values are the transfer source address, the
transfer destination address which were to be transferred subsequently, and the number of remaining
bytes.
When writing these read values to the addresses of SARi, DARi, and TCRi respectively, the same
values are also written to their latches. When setting the DMAi enable bit to “1” under this condition,
transfer of data subsequent to one which has been transferred just before forced termination is
restarted. (Refer to
“Figure 13.3.4-c.”
)
G
In single transfer mode
The remaining data can be transferred by the following procedure:
Read the values at addresses of SARi, DARi and TCRi. Then, rewrite these values into these
addresses.
Set the DMAi enable bit to “1.”
G
In repeat transfer, array chain transfer, and link array chain transfer modes
The remaining data of the block that was interrupted by forced termination can be transferred by
the following procedure:
Switch over the current mode to the single transfer mode.
Read the values at addresses of SARi, DARi and TCRi. Then, rewrite these values into these
addresses.
Set the DMAi enable bit to “1.” (Refer to
“Figure 13.3.4-c.”
)
In order to transfer the next block, switch over the current mode to the previous mode after the
above-mentioned transfer is normally terminated. Then, re-set the values of SARi, DARi, and
TCRi.
In the array chain or the link array chain transfer mode, information such as the next transfer
parameters etc. cannot be read from each latch.