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10.2.4 Interfacing an 8-Bit Device to 16-Bit Memory Using Single-
Address DMA Mode
One of the requirements of single-address mode is that the source and destination must
be the same port size. However, the MC68340 can perform direct memory accesses in
single-address mode between an 8-bit device and 16-bit memory. The port size must be
specified as 8 bits, and some external logic is required as shown in Figure 10-14.
MC68340
Figure 10-14. Circuitry for Interfacing 8-Bit Device to
During even-byte accesses, the data is transferred directly on D15–D8. However, during
odd-byte accesses, the data must be routed on D15–D8 for the 8-bit device and on D7–
D0 for the 16-bit memory.
10.3 POWER CONSUMPTION CONSIDERATIONS
The MC68340 can be designed into low-power applications that involve high-performance
processing capability (32-bits), high functional density, small size, portable capability, and
battery operation.
The MC68340 fits into the following types of applications:
• "Palmtop" Computers
— Stylus Input
— Voice Input
— Image Input
• Transaction Tracking
— Car Rental
— Cargo
— Courier
— Handheld
• Bar Code Scanners
10-10
Freescale Semiconductor, Inc.
DEVICE
D15-D8
R/W
A0
SIZ1
SIZ0
16-Bit Memory in Single-Address DMA Mode
MC68340 USER'S MANUAL
For More Information On This Product,
Go to: www.freescale.com
B
T/R
MEMORY
74F245
OE
A
D7-D0
• Telephony
— Cordless Phones
— Cellular Phones
• CD-I, CD-ROM
• Defense Industry
— Guidance Systems
— Tracking Systems
• Data Entry
• Instruments
• Handheld Games
MOTOROLA
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