
DMA Interface
8-2
MC68322 USER’S MANUAL
MOTOROLA
8.1 DMA CONFIGURATION REGISTERS
The DMA interface provides two internal memory-mapped configuration register sets called
PDMA and GDMA. These registers configure each DMA channel and provide
programmability for transfer address and count. Figure 8-1 illustrates the DMA interface
registers.
Figure 8-1. PDMA and GDMA Configuration Registers
8.1.1 Transfer Address Fields
The PDMA configuration register contains the PDMA DRAM transfer address field. The
GDMA configuration register contains two transfer address fields—GDMA DRAM transfer
address (GDTA) and GDMA chip-select transfer address (GCSTA). These fields define the
base address for the beginning of the transfer and they cannot be written while the BSY bit
in the active channel’s interrupt event register is set. The transfer address fields support the
entire 256M address range of the MC68322.
The GDTA field increments during a DMA transfer. For word-sized data transfers using the
GDMA channel, the transfer address is incremented after every word is transferred. When
receiving byte-sized data, the data is packed into words prior to accessing DRAM and the
address is incremented after every full word is transferred to DRAM. Likewise, for sending
byte-sized data, a word access to DRAM is made, the address in incremented, and the data
is sent unpacked as bytes to the MC68322 bus. All byte-sized data packing is organized as
big endian data.
The MC68322 bus address used for the GDMA channel is fixed and not incremented. The
transfer address for the MC68322 bus is used to access one of eight possible chip-select
banks. The GDMA chip-select transfer address appears on the output address pins of the
MC68322 bus interface (A25–A1). It is assumed the device that is connected to the banks
on the MC68322 bus used for the DMA handles any addressing issues internally.
PDMA CONFIGURATION
REGISTERS
00FFF200
00FFF202
00FFF204
00FFF206
GDMA CONFIGURATION
REGISTERS
00FFF210
00FFF212
00FFF214
00FFF216
00FFF218
00FFF21A
0000
PDMA DRAM TRANSFER ADDRESS ( HIGH WORD)
PDMA TRANSFER COUNT
GDMA TRANSFER COUNT
PDMA DRAM TRANSFER ADDRESS (LOW WORD)
0000
GDMA DRAM TRANSFER ADDRESS (HIGH WORD)
GDMA DRAM TRANSFER ADDRESS (LOW WORD)
GDMA CHIP-SELECT TRANSFER ADDRESS (HIGH WORD)
GDMA CHIP-SELECT TRANSFER ADDRESS (LOW WORD)
FR
= RESERVED
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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