Typewriter User Manual

10-10 MC68340 USER’S MANUAL MOTOROLA
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.
DEVICE
74F245
B
T/R
OE
A
MC68340
MEMORY
D15-D8
SIZ0
SIZ1
A0
R/W
D7-D0
Figure 10-14. Circuitry for Interfacing 8-Bit Device to
16-Bit Memory in Single-Address DMA Mode
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 • Telephony
— Stylus Input — Cordless Phones
— Voice Input — Cellular Phones
— Image Input • CD-I, CD-ROM
• Transaction Tracking • Defense Industry
— Car Rental — Guidance Systems
— Cargo — Tracking Systems
— Courier • Data Entry
— Handheld • Instruments
• Bar Code Scanners • Handheld Games
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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