TC1796
System Units (Vol. 1 of 2)
CPU Subsystem
User’s Manual
2-24
V2.0, 2007-07
CPU, V2.0
2.5
Program Memory Interface (PMI)
Figure 2-11 PMI Block Diagram
2.5.1
PMI Features
The Program Memory Interface (PMI) has the following features:
•
64 Kbyte memory as:
– 16 Kbyte instruction cache (ICACHE)
– 48 Kbyte scratch-pad RAM (SPRAM)
•
ICACHE operation features:
– Two-way set associative cache
– LRU (Least-Recently Used) replacement algorithm
– Cache line size = 256 bits (4 double-words)
– Validity granularity (4 double-words per cache line)
– ICACHE can be globally invalidated to provide support for software cache
coherency (to be handled by the programmer).
– ICACHE can be bypassed to provide a direct fetch from the CPU to on-chip and
off-chip resources.
MCB05595
To/From Program
Local Memory Bus
128
Data Switch
&
Data Alignment
&
Interface Control
PMI
Control
Registers
64
PLMB Interface
Slave
Master
128
CP
U
In
te
rf
a
c
e
64
To/From
CPU
Program Memory
Interface (PMI)
PMEM
Tag
RAM
16 KB
ICACHE
48 KB
SPRAM
To SCU
(PMI Memory Parity Errors)
Parity
Control/Check
PMEM
= Program Memory in PMI
ICACHE = Instruction Cache
SPRAM = Scratch-Pad RAM
PLMB
= Program Local Memory Bus