Burst Buffer Controller 2 Module
MPC561/MPC563 Reference Manual, Rev. 1.2
4-4
Freescale Semiconductor
— No performance penalty during sequential program flow execution
— Minimal performance penalty due to change of program flow execution
•
Two operation modes are available: decompression on and decompression off. Switch between
compressed and non-compressed user application software parts is possible.
•
Adaptive vocabularies scheme is supported; each user application can have its own optimum
vocabularies.
4.1.4
DECRAM Key Features
•
2 Kbytes RAM for decompression vocabulary tables
•
2 clock read/write accesses when used as a U-bus general-purpose RAM
•
4 clock load/store accesses from the L-bus
•
Byte, half-word (16-bit) or word (32-bit) read/write accesses and fetches
•
Special access protection functions
•
Low-power standby operation for data retention
4.1.5
Branch Target Buffer Key Features
•
Consists of eight “branch target entries” (BTE). Each entry contains:
— A 32-bit register that stores the target of historical change of flow (COF) address
— Four RAM entries, 38 bits each, which hold up to four valid instruction OPCODES (32 bits).
The six extra bits are used by ICDU in decompression on mode.
— A 32-bit register that stores the values used to calculate the address following the last valid
instruction.
•
FIFO removal policy management is implemented for the eight BTEs
•
Software-controlled BTB enable/disable and invalidate
•
User transparent (that is, no user management is required)
4.2
Operation Modes
4.2.1
Instruction Fetch
The BBC provides two instruction fetch modes: decompression off and decompression on. The operational
modes are defined by RCPU MSR[DCMPEN] bit. If the bit is set, the mode is decompression on.
Otherwise, it is in decompression off.
4.2.1.1
Decompression Off Mode
In this mode, the BBC bus interface unit (BIU) module transfers fetch accesses from the RCPU to the
U-bus. When a new access is issued by the RCPU, it is transferred in parallel to both the IMPU and the
BIU. The IMPU compares the address of the access to its region programming. The BIU checks if the
access can be immediately transferred to the U-bus, otherwise it requests the U-bus for the next clock.
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...