TC1796
System Units (Vol. 1 of 2)
LMB External Bus Unit
User’s Manual 13-1 V2.0, 2007-07
EBU, V2.0
13 LMB External Bus Unit
The External Bus Unit (EBU) of the TC1796 controls the transactions between external
memories or peripheral units, and the internal memories and peripheral units. The basic
interfaces of the EBU are shown in Figure 13-1.
Figure 13-1 EBU Interface Diagram
The EBU is internally connected to the Program Local Memory Bus (PLMB). This
configuration makes it possible to get fast access times, especially when using external
Burst Flash memory devices.
The following features are supported by the EBU:
• 64-bit internal PLMB interface
• 32-bit external demultiplexed bus interface
– Support for Intel-style and Motorola-style interface signals
– Support for Burst Flash memory devices
– Flexibly programmable access parameters
– Programmable chip select lines
– Arbitration support for external EBU bus master devices
– Little-endian and Big-endian support.
• Scalable external bus frequency
– Derived from PLMB frequency (f
CPU
) divided by 2, 3, or 4
– Maximum 75 MHz
• Data buffering supported
– Code prefetch buffer
– Read/write buffer
External
Bus
Unit
EBU
MCA05712
32
To/From Program
Local Memory Bus
Data Bus
Address Bus
Control Lines
Chip Select
Lines
Clock Output
Clock Input
24
13
5
64
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