
DMA CONTROLLER
13-80
13.8 Link array chain transfer mode
7721 Group User’s Manual
13.8 Link array chain transfer mode
This mode is used to transfer several blocks of data. According to the information of each block stored in
memory area (Note), several blocks of data are transferred. Transfer parameters can be located in separate
memory locations, in a unit of one block’s parameters. Table 13.8.1 lists the specifications of the link array
chain transfer mode, and Figure 13.8.1 shows the register structures of SARi, DARi, and TCRi in this mode.
Note: Each of the following information is called “transfer parameter”: transfer start addresses of transfer
source and destination, and transfer data’s byte number.
Table 13.8.1 Specifications of link array chain transfer mode
Item
Transfer parameter memory
Condition of normal termination
Conditions of forced termination
Interrupt request generation timing
Functions of registers
Performance specifications
Required.
q In 2-bus cycle transfer: 16 bytes per one block
(transfer source’s transfer start address, transfer destination’s transfer
start address, transfer data’s byte number, next transfer parameter
memory’s start address)
q In 1-bus cycle transfer: 12 bytes per one block
(from memory to I/O: transfer source’s transfer start address, transfer
data’s byte number, next transfer parameter memory’s start address)
(from I/O to memory: transfer destination’s transfer start address,
transfer data’s byte number, next transfer parameter memory’s start
address)
SARi latch = 0 and TCRi = 0
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qFalling edge of TC pin’s input from “H” to “L”
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(when the TC pin validity bit = “1”)
qWrite “0” to the DMAi enable bit
At normal termination
SARi latch: Indicates the transfer parameter memory’s start address of
the next block.
SARi: Indicates the address of the next transfer source.
DARi latch: Not used.
DARi: Indicates the address of the next transfer destination.
TCRi latch: Not used.
TCRi: Indicates the number of remaining bytes being transferred.
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TC
pin validity bit: Bit 1 at address 6816