Motorola MSC8101 ADS User's Guide Page 119

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Initializing the DMA
DMA Channels 6-11
The BD_ATTR bits are as follows.
Some of the bit functions are straightforward:
INTRPT defines whether the DMA issues an interrupt when BD_SIZE reaches
zero.
NO_INC defines the constant address for port access applications.
TSZ determines the transfer size.
FLS indicates whether the FIFO is flushed when BD_SIZE reaches zero.
RD must be set if data should be read from the buffer.
Other BD_ATTR bits work together in a particular mode. CYC, NBUS, and NBD must be
considered if CONT is set. CONT defines whether the buffer is closed when the transfer is
complete or whether the DMA transaction continues when BD_SIZE reaches zero. If a
continuous buffer is chosen (CONT=1), then BD_SIZE is reloaded with a BD_BSIZE
value. CYC defines whether BD_ADDR is a cyclic address. NBUS defines which bus is
used for the next transaction, and NBD defines the next buffer to be used.
BD_SIZE Size
A transfer byte size down counter. BD_SIZE is always the number of bytes left to transfer even
though the transfer size parameter may vary between eight bits to one burst.
BD_BSIZE Base Size
Required only for programming continuous buffers. When the DMA transfer size reaches zero (the
complete buffer is transferred), BD_SIZE is updated with the value of the BD_BSIZE parameter, and
the transfer can resume.
BD_ATTR Attributes
Defines the buffer characteristics.
BD_ATTR Buffer Attributes Parameter
Bit 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
INTRPT CYC CONT —NO_INC BP NBUS NBD
TYPE R/W
RESET Undefined
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
TSZ FLS RD TC GBL
TYPE R/W
RESET Undefined
Table 6-4. Buffer Descriptor Parameters (Continued)
Parameter Description
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