IDMA Channels
7-46
MC68360 USER’S MANUAL
Figure 7-13. Dual Address Transfer Example
Dual Address Destination Write
. During this type of IDMA cycle, the data in the DHR is
written to the device or memory selected by the address in the DAPR, the destination func-
tion codes in the FCR, and the size in the CMR. The same options exist for operand size
and alignment as in the dual address source read. When the complete operand is written,
the DAPR is incremented by 1, 2, or 4, according to the DAPI and DSIZE bits of the CMR,
and the BTC is decremented by the number of bytes transferred. If the BTC is equal to zero,
the DONEx signal for the IDMA handshake is asserted, and if the transfer is completed with
no errors, the DONE bit in the CSR is set. See 7.5.2.4 Timer Reference Registers (TRR1,
TRR2, TRR3, TRR4) and 7.6.2.6 Byte Count Register (BCR) for more information.
Dual Address Packing
. When dual address mode is selected, the IDMA can perform pack-
ing. Regardless of the source size, destination size, source starting address, or destination
starting address, the IDMA will use the most efficient packing algorithm possible to perform
the transfer in the fewest possible number of bus cycles.
NOTE
The packing algorithms are subject to the restriction that the
IDMA never performs 3-byte transfers.
Three examples of the packing technique follow.
Example 1. This simple example shows how packing is performed when the source and des-
tination sizes are the same—word. The source address is $00000001, and the destination
address is $20000000. The number of bytes to be transferred is 4.
IDMA channel 1 initialization required for this example:
—ICCR = $0720. Recommended normal configuration.
—FCR1 = $89. Source function code is 1000; destination function code is 1001.
—SAPR1 = $00000001. Source address.
—DAPR1 = $20000000. Destination address.
—BCR1 = $00000003. Byte transfer count.
PERIPHERAL
MEMORY
1
2
DHR
TWO BUS CYCLES
REQUIRED
DATA
BUS
DACKx
AND
ADDR.
QUICC
IDMA
1
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
..
.