AN2008 Motorola / Freescale Semiconductor, AN2008 Datasheet - Page 3

• Manufacturer Part Number: AN2008
• Description: Evaluating ColdFire in a 68K Target System: MCF5307 to MC68EC020 Gateway Reference Design
• Manufacturer: Motorola / Freescale Semiconductor

1.1 Design Considerations
The MC68EC020 is a low-cost, (high performance) embedded derivative of the popular 32-bit MC68020
Microprocessor. The major differences between the MC68020 and the MC68EC020 is that the MC68EC020
has a 24-bit address bus and does not implement the /ECS, /OCS, /DBEN, /IPEND or /BGACK signals.
Address
Address
pads
bus
24-bit
Sequencer and Control
Instruction
Control store
Control logic
Address
address
Write pending
bus
bus
buffer
Bus control signals
MCF5307 to MC68EC020 Gateway Reference Design
Microbus control
logic
Program
counter
section
Figure 1. MC68EC020 Block Diagram
Prefetch pending
Bus Controller
Stage
buffer
D
Instruction Pipe
Address
section
Stage
Execution Unit
C
Misalignment
multiplexer
Instruction
section
Stage
cache
Data
B
(CAHR)
register
holding
Cache
Multiplexer
Design Considerations
Data
pads
Size
32-bit
Internal
data
bus
Data
bus
3