2/24/2008 9T6WP
Preliminary Hardware Data Module
BCM7405
06/29/07
Functional Description
Bro a d c o m Co rp o r a ti o n
Document
7405-1HDM00-R
MIPS4380 Processor Core Page 1-65
M
AJOR
F
UNCTIONAL
B
LOCKS
depicts a block diagram of the CPU. An overview of these functional blocks is presented in this section.
Figure 1-16: Block Diagram of the CPU
Execution Unit
Each thread processor (TP) can execute the following types of instructions:
1
an ALU for logical, shift, add, and subtract operations,
2
a MDU for multiply, divide, 32-bit and 16-bit (eDSP) multiply-accumulate operations,
3
a MIPS16e unit to decode 16-bit instructions to 32-bit instructions for execution,
4
a Floating-Point Unit (FPU), and
5
generates the address of a load/store instruction.
The processor core contains thirty-two 32-bit general-purpose registers used for scalar integer operations, address
calculation and translation from virtual to physical. The register file is fully bypassed to minimize latency in the six-stage
pipeline.
The execution unit includes:
•
Branch unit for branch resolution and next instruction calculation
•
MIPS32 and MIPS16e instruction decoding units
•
ALU for performing the 32-bit and 16-bit (MIPS16e) arithmetic, shift, and logical operations.
•
Address unit with a 32-bit adder used for calculating the next operand address
•
Load and store aligners of partial word accesses
PerfCtr
CP0
s
TP
0
Terms:
RAC- ReadAhead Cache
eDSP - 16-bit DSP Extension
JTLB - Translation Lookaside Buffer
ALU - ISA decode & execution units
CP0
l
/CP0
s
- CP0 local and shared registers
GPR - General Purpose Registers
S MISB
LMB
BIU
EJTAG
D-Cache
RAC
MDU
eDSP
BIU - Bus (System) Interface Unit
LMB - Low-latency Memory Bus
64b
FPR
0
FPR/FCR - FPU General & Control Registers
PerfCtr - Performance Counters
FPU/FPE - Floating-Point Unit & Engine
MDU - Multiply-Divide Unit
MIPS16e - 16-bit Compression ISA
EJTAG/DSU - Debug Unit
I-Cache
0
GPR
MIPS16e
ALU
CP0
l
TP
1
DSU
I-Cache
1
JTLB
FPR
1
FCR
1
FCR
0
L2 Cache
FPU
FPE
CP 1
GPR
MIPS16e
ALU
CP0
l
JTLB
CP 1
CP1- Coprocessor 1 Interface to the FPU
SMISB - Split-transaction MISB System B us
256b
System/
Memory
Mem ory