Datasheet ACT-7000SC-225F17M, ACT-7000SC-210F17T, ACT-7000SC-200F17C, ACT-7000SC Datasheet (ACT)

ACT 7000SC

64-Bit Superscaler Microprocessor

Features

■

Full militarized QED RM7000 microprocessor

■

Dual Issue symmetric superscalar microprocessor with
instruction prefetch optimized for system level
price/performance

●

150, 200, 210, 225 MHz operating frequency

Consult Factory for latest speeds

●

MIPS IV Superset Instruction Set Architecture

■

High performance interface (RM52xx compatible)

●

600 MB per second peak throughput

●

75 MHz max. freq., multiplexed address/data

●

Supports 1/2 clock multipliers (2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9)

●

IEEE 1149.1 JTAG (TAP) boundary scan

■

Integrated primary and secondary caches - all are 4-way set
associative with 32 byte line size

●

16KB instruction

●

16KB data: non-blocking and write-back or write-through

●

256KB on-chip secondary: unified, non-blocking, block writeback

■

MIPS IV instruction set

●

Data PREFETCH instruction allows the processor to overlap cache

miss latency and instruction execution

●

Floating point combined multiply-add instruction increases

performance in signal processing and graphics applications

●

Conditional moves reduce branch frequency

●

Index address modes (register + register)

■

Embedded supply de-coupling capacitors and additional PLL
filter components

■

Integrated memory management unit (ACT52xx compatible)

●

Fully associative joint TLB (shared by I and D translations)

●

48 dual entries map 96 pages

●

4 entry DTLB and 4 entry ITLB

●

Variable page size (4KB to 16MB in 4x increments)

■

Embedded application enhancements

●

Specialized DSP integer Multiply-Accumulate instruction,
(MAD/MADU) and three-operand multiply instruction (MUL/U)

●

Per line cache locking in primaries and secondary

●

Bypass secondary cache option

●

I&D Test/Break-point (Watch) registers for emulation & debug

●

Performance counter for system and software tuning & debug

●

Ten fully prioritized vectored interrupts - 6 external, 2 internal, 2
software

●

Fast Hit-Writeback-Invalidate and Hit-Invalidate cache operations
for efficient cache management

■

High-performance floating point unit - 600 M FLOPS
maximum

●

Single cycle repeat rate for common single-precision operations
and some double-precision operations

●

Single cycle repeat rate for single-precision combined multiply­add operations

●

Two cycle repeat rate for double-precision multiply and
double-precision combined multiply-add operations

■

Fully static CMOS design with dynamic power down logic

●

Standby reduced power mode with WAIT instruction

●

4 watts typical @ 2.5V Int., 3.3V I/O, 200MHz

■

208-lead CQFP, cavity-up package (F17)

■

208-lead CQFP, inverted footprint (F24), with the same pin
rotation as the commercial QED RM5261

BLOCK DIAGRAM

Store Buffer

Packer / Unpacker

MultAdd, Add, Sub,

Secondary Tags

Set A

Primary Data Cache

4 - Way Set Associative

Write Buffer

Read Buffer

D Bus

Floating-Point

Load /Align

Floating-Point

Register File

Comparator

Floating-Point

Cvt, Div, Sqrt

Multiplier Array

On -Chip 256K Byte Secondary Cache, 4 -Way Set Associative

Secondary Tags

Set B

System /Memory

Floating -Point Control

DTag

DTLB

Pad Buffer

Address Buffer

Joint TLB

Coprocessor 0

Control

PC Incrementer

Branch PC Adder

ITLB Virtuals

Program Counter

Secondary Tags

ITag

ITLB

DVA

IVA

Set C

Primar y Instruction Cache

F-Pipe Bus

Load Aligner

Integer Register File

M Pipe F Pipe

Adder

StAin/Sh Shifter

FA Bus

DTLB Virtuals

Secondary Tags

Set D

4 -Way Set Associative

A/D Bus

Prefetch Buffer

Instruction Dispatch Unit

F Pipe Register

M Pipe Register

Int Mult. Div. MaddPLL/Clocks

Pad Bus

M-Pipe Bus

Adder

LogicalsLogicals

Integer Control

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Technology

– MIPS RISC Microprocessors © SCD7000SC REV B 7/30/01

DESCRIPTION

The ACT 7000SC is a highly integrated symmetric
superscalar microprocessor capable of issuing two
instructions each processor cycle. It has two high
performance 64-bit integer units as well as a high
throughput, fully pipelined 64-bit floating point unit. To
keep its multiple execution units running efficiently,
the ACT 7000SC integrates not only 16KB 4-way set
associative instruction and data caches but backs
them up with an integrated 256KB 4-way set
associative secondary as well. For maximum
efficiency, the data and secondary caches are
writeback and nonblocking. A RM52XX family
compatible, operating system friendly memory
management unit with a 64 / 48-entry fully associative
TLB and a high-performance 64-bit system interface
supporting hardware prioritized and vectored
interrupts round out the main features of the
processor.

The ACT 7000SC is ideally suited for highend
embedded control applications such as
internetworking, high performance image
manipulation, high speed printing, and 3-D
visualization.

HARDWARE OVERVIEW

The ACT 7000SC offers a high-level of integration
targeted at high-performance embedded
applications. The key elements of the ACT 7000SC
are briefly described below.

CPU Registers

Like all MIPS ISA processors, the ACT 7000SC
CPU has a simple, clean user visible state consisting
of 32 general purpose registers, or GPR’s, two special
purpose registers for integer multiplication and
division, and a program counter; there are no
condition code bits. Figure 1 shows the user visible
state.

Superscalar Dispatch

The ACT 7000SC has an efficient symmetric
superscalar dispatch unit which allows it to issue up to
two instructions per cycle. For purposes of instruction
issue, the ACT 7000SC defines four classes of
instructions: integer, load/store, branches, and
floating-point. There are two logical pipelines, the

function

, or F, pipeline and the

memory

, or M,
pipeline. Note however that the M pipe can execute
integer as well as memory type instructions.

Table 1 – Instruction Issue Rules

F Pipe M Pipe

one of: one of:

integer, branch, floating-point,

integer mul, div

Figure 2 is a simplification of the pipeline section
and illustrates the basics of the instruction issue
mechanism.

integer, load/store

General Purpose Registers

63 0 Multiply/Divide Registers

063

r1 HI

r2 63

•LO

•

• Program Counter

•63

r29 PC

r30

r31

0

0

0

Figure 1 – CP0 Registers

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.

Table 2 – Dual Issue Instruction Classes

Instruction

Cache

Dispatch

Unit

F Pipe IBus

M Pipe IBus

FP

F Pipe

FP

M Pipe

Integer

F Pipe

Integer
M Pipe

Figure 2 – Instruction Issue Paradigm

The figure illustrates that one F pipe instruction and
one M pipe instruction can be issued concurrently but
that two M pipe or two F pipe instructions cannot be
issued. Table 2 specifies more completely the
instructions within each class.

integer load/store floating-point branch

add, sub, or, xor,

shift, etc.

lw, sw, ld, sd,

ldc1, sdc1,

mov, movc,

fmov, etc.

fadd, fsub, fmult,

fmadd, fdiv, fcmp,

fsqrt, etc.

beq, bne,

bCzT, bCzF, j,

etc.

The symmetric superscalar capability of the ACT
7000SC, in combination with its low latency integer
execution units and high-throughput fully pipelined
floating-point execution unit, provides unparalleled
price/performance in computational intensive
embedded applications.

Pipeline

The logical length of both the F and M pipelines is
five stages with state committing in the register write,
or W, pipe stage. The physical length of the
floating-point execution pipeline is actually seven
stages but this is completely transparent to the user.

Figure 3 shows instruction execution within the
ACT 7000SC when instructions are issuing
simultaneously down both pipelines. As illustrated in
the figure, up to ten instructions can be executing
simultaneously. This figure presents a somewhat
simplistic view of the processors operation however
since the out-of-order completion of loads, stores, and

I0 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W

I1 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W

I2 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W

I3 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W

I4 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W
I5 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W

I6 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W
I7 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W

I8 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W
I9 1l 2l 1R 2R 1A 2A 1D 2D 1W 2W

one cycle

Instruction cache access

1I-1R:

Instruction virtual to physical address translation

2I:

Register file read, Bypass calculation, Instruction decode, Branch address calculation

2R:

Issue or slip decision, Branch decision

1A:

Data vir tual address calculation

1A:

Integer add, logical, shift

1A-2A:

Store Align

2A:

Data cache access and load align

2A-2D:

Data virtual to physical address translation

1D:

Register file write

2W:

Figure 3 – Pipeline

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long latency floating-point operations can result in

Table 3 – ALU Operations

there being even more instructions in process than
what is shown.

Note that instruction dependencies, resource
conflicts, and branches result in some of the
instruction slots being occupied by NOPs.

Integer Unit

Like the ACT 52xx family, the ACT 7000SC

Unit F Pipe M Pipe

Adder add, sub add, sub, data address

add

Logic logic, moves, zero shifts

(nop)

Shifter non zero shift non zero shift, store

logic, moves, zero shifts

(nop)

align

implements the MIPS IV Instruction Set Architecture,
and is therefore fully upward compatible with
applications that run on processors such as the
R4650 and R4700 that implement the earlier
generation MIPS III Instruction Set Architecture.
Additionally, the ACT 7000SC includes two
implementation specific instructions not found in the
baseline MIPS IV ISA, but that are useful in the

Integer Multiply/Divide

The ACT 7000SC has a single dedicated integer
multiply/divide unit optimized for high-speed multiply
and multiply-accumulate operations. The
multiply/divide unit resides in the F type execution
unit. Table 4 shows the performance of the
multiply/divide unit on each operation.

embedded market place. Described in detail in a later
section of this datasheet, these instructions are
integer multiply-accumulate and three-operand
integer multiply.

The ACT 7000SC integer unit includes thirty-two
general purpose 64-bit registers, the HI/LO result
registers for the two-Pipeline operand integer
multiply/divide operations, and the program counter,
or PC. There are two separate execution units, one of
which can execute function, or F, type instructions
and one which can execute memory, or M, type
instructions. See above for a description of the
instruction types and the issue rules. As a special
case, integer multiply/divide instructions as well as
their corresponding MFHi and MFLo instructions can

Table 4 – Integer Multiply/ Divide Operations

Operand

Opcode

MULT/U,

MAD/U

MUL 16 bit 4 3 2

DMULT,

DMULTU

DIV, DIVD any 36 36 0

DDIV,

DDIVU

Size Latency

16 bit 4 3 0

32 bit 5 4 0

32 bit 5 4 3

any980

any 68 68 0

Repeat

Rate

Cycles

only be executed in the F type execution unit. Within
each execution unit the operational characteristics
are the same as on previous QED designs with single
cycle ALU operations (add, sub, logical, shift), one
cycle load delay, and an autonomous multiply/divide
unit.

The baseline MIPS IV ISA specifies that the results
of a multiply or divide operation be placed in the Hi
and Lo registers. These values can then be
transferred to the general purpose register file using
the Move-from-Hi and Move-from-Lo (MFHI/MFLO)
instructions.

Register File

The ACT 7000SC has thirty-two general purpose
registers with register location (r0) hard wired to zero
value. These registers are used for scalar integer
operations and address calculation. In order to
service the two integer execution units, the register
file has four read ports and two write ports and is fully
bypassed both within and between the two execution
units to minimize operation latency in the pipeline.

In addition to the baseline MIPS IV integer multiply
instructions, the ACT 7000SC also implements the
3-operand multiply instruction, MUL. This instruction
specifies that the multiply result go directly to the
integer register file rather than the Lo register. The
portion of the multiply that would have normally gone
into the Hi register is discarded. For applications
where it is known that the upper half of the multiply
result is not required, using the MUL instruction
eliminates the necessity of executing an explicit

ALU

The ACT 7000SC has two complete integer ALU’s
each consisting of an integer adder/subtractor, a logic
unit, and a shifter. Table 3 shows the functions
performed by the ALU’s for each execution unit. Each
of these units is optimized to perform all operations in
a single processor cycle.

MFLO instruction.

Also included in the ACT 7000SC are the
multiply-add instructions MAD/MADU. This
instruction multiplies two operands and adds the
resulting product to the current contents of the Hi and
Lo registers. The multiply-accumulate operation is the
core primitive of almost all signal processing
algorithms allowing the ACT 7000SC to eliminate the
need for a separate DSP engine in many embedded
applications.

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Stall

By pipelining the multiply-accumulate function and

dynamically determining the size of the input

Table 5 – Floating Point Latencies and

Repeat Rates

operands, the ACT 7000SC is able to maximize
throughput while still using an area efficient
implementation.

Floating-Point Coprocessor

The ACT 7000SC incorporates a high-performance
fully pipe-lined floating-point coprocessor which
includes a floating-point register file and autonomous
execution units for multiply/ add/convert and
divide/square root. The floating-point coprocessor is a
tightly coupled co-execution unit, decoding and
executing instructions in parallel with, and in the case
of floating-point loads and stores, in cooperation with
the M pipe of the integer unit. As described earlier, the
superscalar capabilities of the ACT 7000SC allow
floating-point computation instructions to issue
concurrently with integer instructions.

Floating-Point Unit

The ACT 7000SC floating-point execution unit
supports single and double precision arithmetic, as
specified in the IEEE Standard 754. The execution
unit is broken into a separate divide/square root unit
and a pipelined multiply/add unit. Overlap of
divide/square root and multiply/add is supported.

The ACT 7000SC maintains fully precise
floating-point exceptions while allowing both
overlapped and pipelined operations. Precise
exceptions are extremely important in object-oriented
programming environments and highly desirable for

Operation

fadd 4 1

fsub 4 1

fmult 4/5 1/2

fmadd 4/5 1/2

fmsub 4/5 1/2

fdiv 21/36 19/34

fsqrt 21/36 19/34

frecip 21/36 19/34

frsqrt 38/68 36/66

fcvt.s.d 4 1

fcvt.s.w 6 3

fcvt.s.l 6 3

fcvt.d.s 4 1

fcvt.d.w 4 1

fcvt.d.l 4 1

fcvt.w.s 4 1

fcvt.w.d 4 1

fcvt.l.s 4 1

fcvt.l.d 4 1

fcmp 1 1

fmov, fmovc 1 1

fabs, fneg 1 1

Latency

single/double

Repeat Rate

single/double

debugging in any environment.

The floating-point unit’s operation set includes
floating-point add, subtract, multiply, multiply-add,
divide, square root, reciprocal, reciprocal square root,
conditional moves, conversion between fixed-point
and floating-point format, conversion between
floating-point formats, and floating-point compare.
Table 5 gives the latencies of the floating-point
instructions in internal processor cycles.

To support superscalar operations, the FGR has
four read ports and two write ports, and is fully
bypassed to minimize operation latency in the
pipeline. Three of the read ports and one write port
are used to support the combined multiply-add
instruction while the fourth read and second write port
allows a concurrent floating-point load or store and
conditional moves.

System Control Coprocessor (CP0)

Floating-Point General Register File

The floating-point general register file, FGR, is
made up of thirty-two 64-bit registers. With the
floating-point load and store double instructions,
LDC1 and SDC1, the floating-point unit can take
advantage of the 64-bit wide data cache and issue a
floating-point coprocessor load or store double-word
instruction in every cycle.

The floating-point control register file contains two
registers; one for determining configuration and
revision information for the coprocessor and one for
control and status information. These registers are
primarily used for diagnostic software, exception
handling, state saving and restoring, and control of
rounding modes.

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The system control coprocessor (CP0) in the MIPS
architecture is responsible for the virtual memory
sub-system, the exception control system, and the
diagnostics capability of the processor. In the MIPS
architecture, the system control coprocessor (and
thus the kernel software) is implementation
dependent. For memory management, the ACT
7000SC CP0 is logically identical to that of the
RM5200 Family and R5000. For interrupt exceptions
and diagnostics, the ACT 7000SC is a superset of the
RM5200 Family and R5000 implementing additional
features described later in the sections on Interrupts,
the Test/Breakpoint facility, and the Performance
Counter facility.

The memory management unit controls the virtual
memory system page mapping. It consists of an
instruction address translation buffer, or ITLB, a data

5

address translation buffer, or DTLB, a Joint TLB, or
JTLB, and coprocessor registers used by the virtual
memory mapping sub-system.

System Control Coprocessor Registers

The ACT 7000SC incorporates all system control
coprocessor (CP0) registers internally. These
registers provide the path through which the virtual
memory system’s page mapping is examined and
modified, exceptions are handled, and operating
modes are controlled (kernel vs. user mode,
interrupts enabled or disabled, cache features). In
addition, the ACT 7000SC includes registers to
implement a real-time cycle counting facility, to aid in
cache and system diagnostics, and to assist in data
error detection.

To support the non-blocking caches and enhanced
interrupt handling capabilities of the ACT 7000SC,
both the data and control register spaces of CP0 are
supported by the ACT 7000SC. In the data register
space, that is the space accessed using the MFC0
and MTC0 instructions, the ACT 7000SC supports the
same registers as found in the RM5200, R4000 and
R5000 families. In the control space, that is the space
accessed by the previously unused CTC0 and CFC0
instructions, the ACT 7000SC supports five new
registers. The first three of these new 32-bit registers
support the enhanced interrupt handling capabilities
and are the Interrupt Control, Interrupt Priority Level
Lo (IPLLO), and Interrupt Priority Level Hi (IPLHI)

registers. These registers are described further in the
section on interrupt handling. The other two registers,

Imprecise Error 1

and

Imprecise Error 2

, have been
added to help diagnose bus errors which occur on
non-blocking memory references.

Figure 4 shows the CP0 registers.

Virtual to Physical Address Mapping

The ACT 7000SC provides three modes of virtual

addressing:

• user mode

• supervisor mode

• kernel mode

This mechanism is available to system software to
provide a secure environment for user processes. Bits
in the CP0 Status register determine which virtual
addressing mode is used. In the user mode, the ACT
7000SC provides a single, uniform virtual address
space of 256GB (2GB in 32-bit mode).

When operating in the kernel mode, four distinct
virtual address spaces, totalling 1024GB (4GB in
32-bit mode), are simultaneously available and are
differentiated by the high-order bits of the virtual
address.

The ACT 7000SC processor also supports a
supervisor mode in which the virtual address space is

256.5GB (2.5GB in 32-bit mode), divided into three
regions based on the high-order bits of the virtual
address. Figure 5 shows the address space layout for
32-bit operation.

LLAddr

17*

PageMask

5*

EntryHi

10*

47

(entries protected

from TLBWR)

0

TagLo

28*

EntryLo0

2*

EntryLo1

3*

TLB

TagHi

29*

Used for memory

management

Context

Info

7*

Index

0*

Random

1*

Wired

6*

PRid

15*

Config

16*

* Registered number

Status

Watch2

4*

Count

9*

12*

EPC

14*

19*

ECC

26*

BadVAddr

8*

Compare

11*

Cause

13*

Watch1

18*

Xcontext

20*

CacheErr

27*

ErrorEPC

30*

Used for exception

processing

Perf Counter

25*

Perf Ctr Cntrl

22*

Watch Mask

24*

IPLLO

18*

IPLHI

19*

IntControl

20*

Imp Error 1

26*

Imp Error 2

27*

Control Space Registers

Figure 4 – CP0 Registers

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Figure 5 – Kernel Mode Virtual Addressing

(32-bit mode)

is loaded with the desired page size of a mapping,
and that size is stored into the TLB along with the
virtual address when a new entry is written. Thus,

0xFFFFFFFF Kernel virtual address space

(kseg3)
Mapped, 0.5GB

0xE0000000

0xDFFFFFFF Supervisor virtual address space

(ksseg)
Mapped, 0.5GB

0xC0000000

0xBFFFFFFF Uncached kernel physical address space

(kseg1)
Unmapped, 0.5GB

0xA0000000

0x9FFFFFFF Cached kernel physical address space

(kseg0)
Unmapped, 0.5GB

0x80000000

0x7FFFFFFF User virtual address space

(kuseg)
Mapped, 2.0GB

operating systems can create special purpose maps;
for example, a typical frame buffer can be memory
mapped using only one TLB entry.

The second mechanism controls the replacement
algorithm when a TLB miss occurs. The ACT 7000SC
provides a random replacement algorithm to select a
TLB entry to be written with a new mapping; however,
the processor also provides a mechanism whereby a
system specific number of mappings can be locked
into the TLB, thereby avoiding random replacement.
This mechanism allows the operating system to
guarantee that certain pages are always mapped for
performance reasons and for deadlock avoidance.
This mechanism also facilitates the design of
real-time systems by allowing deterministic access to
critical software.

The JTLB also contains information that controls
the cache coherency protocol for each page.
Specifically, each page has attribute bits to determine
whether the coherency algorithm is: uncached,
write-back, write-through with write-allocate,
write-through without write-allocate, write-back with
secondary bypass. Note that both of the write-through
protocols bypass the secondary cache since it does
not support writes of less than a complete cache line.

These protocols are used for both code and data on
the ACT 7000SC with data using write-back or
write-through depending on the application. The
write-through modes support the same efficient frame
buffer handling as the RM5200 Family, R4700 and
R5000.

0x00000000

Instruction TLB

The ACT 7000SC uses a 4-entry instruction TLB

When the ACT 7000SC is configured for 64-bit
addressing, the virtual address space layout is an
upward compatible extension of the 32-bit virtual
address space layout.

Joint TLB

For fast virtual-to-physical address translation, the
ACT 7000SC uses a large, fully associative TLB that
maps virtual pages to their corresponding physical
addresses. As indicated by its name, the joint TLB
(JTLB) is used for both instruction and data
translations. The JTLB is organized as pairs of
even/odd entries, and maps a virtual address and
address space identifier into the large, 64GB physical
address space. By default, the JTLB is configured as
48 pairs of even/odd entries. The 64 even/odd entry
optional configuration is set at boot time.

Two mechanisms are provided to assist in
controlling the amount of mapped space, and the
replacement characteristics of various memory
regions. First, the page size can be configured, on a
per-entry basis, to use page sizes in the range of 4KB
to 16MB (in 4X multiples). A CP0 register, PageMask,

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(ITLB) to minimize contention for the JTLB, to
eliminate the critical path of translating through a
large associative array, and to save power. Each ITLB
entry maps a 4KB page. The ITLB improves
performance by allowing instruction address
translation to occur in parallel with data address
translation. When a miss occurs on an instruction
address translation by the ITLB, the least-recently
used ITLB entry is filled from the JTLB. The operation
of the ITLB is completely transparent to the user.

Data TLB

The ACT 7000SC uses a 4-entry data TLB (DTLB)
for the same reasons cited above for the ITLB. Each
DTLB entry maps a 4KB page. The DTLB improves
performance by allowing data address translation to
occur in parallel with instruction address translation.
When a miss occurs on a data address translation by
the DTLB, the DTLB is filled from the JTLB. The DTLB
refill is pseudo-LRU: the least recently used entry of
the least recently used pair of entries is filled. The
operation of the DTLB is completely transparent to the
user.

7

Cache Memory

In order to keep the ACT 7000SC’s superscalar
pipeline full and operating efficiently, the ACT
7000SC has integrated primary instruction and data
caches with single cycle access as well as a large
unified secondary cache with a three cycle miss
penalty from the primaries. Each primary cache has a
64-bit read path, a 128-bit write path, and both caches
can be accessed simultaneously. The primary caches
provide the integer and floating-point units with an
aggregate band-width of 3.6 GB per second at an
internal clock frequency of 225 MHz. During an
instruction or data primary cache refill, the secondary
cache can provide a 64-bit datum every cycle
following the initial three cycle latency for a peak
bandwidth of 2.4 GB per second.

Instruction Cache

The ACT 7000SC has an integrated 16KB,
four-way set associative instruction cache and, even
though instruction address translation is done in
parallel with the cache access, the combination of
4-way set associativity and 16KB size results in a
cache which is virtually indexed and physically
tagged. Since the effective physical index eliminates
the potential for virtual aliases in the cache, it is
possible that some operating system code can be
simplified as compared with the RM5200 Family,
R5000 and R4000 class processors.

The data array portion of the instruction cache is 64
bits wide and protected by word parity while the tag
array holds a 24-bit physical address, 14
housekeeping bits, a valid bit, and a single bit of parity
protection.

By accessing 64 bits per cycle, the instruction
cache is able to supply two instructions per cycle to
the superscalar dispatch unit. For signal processing,
graphics, and other numerical code sequences where
a floating-point load or store and a floating-point
computation instruction are being issued together in a
loop, the entire bandwidth available from the
instruction cache will be consumed by instruction
issue. For typical integer code mixes, where
instruction dependencies and other resource
constraints restrict the achievable parallelism, the
extra instruction cache bandwidth is used to fetch
both the taken and non-taken branch paths to
minimize the overall penalty for branches. A 32-byte
(eight instruction) line size is used to maximize the
communication efficiency between the instruction
cache and the secondary cache, or memory system.

The ACT 7000SC is the first MIPS RISC
microprocessor to support cache locking on a per line
basis. The contents of each line of the cache can be
locked by setting a bit in the Tag. Locking the line
prevents its contents from being overwritten by a
subsequent cache miss. Refill will occur only into
unlocked cache lines. This mechanism allows the
programmer to lock critical code into the cache

locked code sequence.

Data Cache

The ACT 7000SC has an integrated 16KB,
four-way set associative data cache, and even though
data address translation is done in parallel with the
cache access, the combination of 4-way set
associativity and 16KB size results in a cache which
is physically indexed and physically tagged. Since the
effective physical index eliminates the potential for
virtual aliases in the cache, it is possible that some
operating system code can be simplified compared to
the RM5200 Family, R5000 and R4000 class
processors. The data cache is non-blocking; that is, a
miss in the data cache will not necessarily stall the
processor pipeline. As long as no instruction is
encountered which is dependent on the data
reference which caused the miss, the pipeline will
continue to advance. Once there are two cache
misses outstanding, the processor will stall if it
encounters another load or store instruction. A
32-byte (eight word) line size is used to maximize the
communication efficiency between the data cache
and the secondary cache or memory system. The
data array portion of the data cache is 64 bits wide
and protected by byte parity while the tag array holds
a 24-bit physical address, 3 housekeeping bits, a two
bit cache state field, and has two bits of parity
protection. The normal write policy is write-back,
which means that a store to a cache line does not
immediately cause memory to be updated. This
increases system performance by reducing bus traffic
and eliminating the bottleneck of waiting for each
store operation to finish before issuing a subsequent
memory operation. Software can, however, select
write-through on a per-page basis when appropriate,
such as for frame buffers. Cache protocols supported
for the data cache are:

1. Uncached. Reads to addresses in a memory
area identified as uncached will not access the
cache. Writes to such addresses will be written
directly to main memory without updating the
cache.

2. Write-back. Loads and instruction fetches will
first search the cache, reading the next memory
hierarchy level only if the desired data is not
cache resident. On data store operations, the
cache is first searched to determine if the target
address is cache resident. If it is resident, the
cache contents will be updated, and the cache
line marked for later write-back. If the cache
lookup misses, the target line is first brought into
the cache and then the write is performed as
above.

3. Write-through with write allocate. Loads and
instruction fetches will first search the cache,
reading from memory only if the desired data is
not cache resident; write-through data is never
cached in the secondary cache. On data store

thereby guaranteeing deterministic behavior for the

Aeroflex Circuit Technology SCD7000SC REV B 7/30/01 Plainview NY [phone]

8

operations, the cache is first searched to
determine if the target address is cache
resident. If it is resident, the primary cache
contents will be updated and main memory will
also be written leaving the write-back bit of the
cache line unchanged; no writes will occur into
the secondary. If the cache lookup misses, the
target line is first brought into the cache and then
the write is performed as above.

4. Write-through without write allocate. Loads
and instruction fetches will first search the
cache, reading from memory only if the desired
data is not cache resident; write-through data is
never cached in the secondary. On data store
operations, the cache is first searched to
determine if the target address is cache
resident. If it is resident, the cache contents will
be updated and main memory will also be
written leaving the write-back bit of the cache
line unchanged; no writes will occur into the
secondary. If the cache lookup misses, then
only main memory is written.

5. Write-back with secondary bypass. Loads and
instruction fetches first search the primary
cache, reading from memory only if the desired
data is not resident; the secondary is not
searched. On data store operations, the primary
cache is first searched to determine if the target
address is resident. If it is resident, the cache
contents are updated, and the cache line
marked for later write-back. If the cache lookup
misses, the target line is first brought into the
cache and then the write is performed as above.

Associated with the Data Cache is the store buffer.
When the ACT 7000SC executes a STORE
instruction, this single-entry buffer gets written with
the store data while the tag comparison is performed.
If the tag matches, then the data is written into the
Data Cache in the next cycle that the Data Cache is
not accessed (the next non-load cycle). The store
buffer allows the ACT 7000SC to execute a store
every processor cycle and to perform back-to-back
stores without penalty. In the event of a store
immediately followed by a load to the same address,
a combined merge and cache write will occur such
that no penalty is incurred.

Secondary Cache

The ACT 7000SC has an integrated 256KB,
four-way set associative, block write-back secondary
cache. The secondary has the same line size as the
primaries, 32 bytes, is logically 64-bits wide matching
the system interface and primary widths, and is
protected with doubleword parity. The secondary tag
array holds a 20-bit physical address, 2 housekeeping
bits, a three bit cache state field, and two parity bits.

By integrating a secondary cache, the ACT 7000SC
is able to dramatically decrease the latency of a
primary cache miss without dramatically increasing

Aeroflex Circuit Technology SCD7000SC REV B 7/30/01 Plainview NY [phone]

the number of pins and the amount of power required
by the processor. From a technology point of view,
integrating a secondary cache maximally leverages
CMOS semiconductor technology by using silicon to
build the structures that are most amenable to silicon
technology; silicon is being used to build very dense,
low power memory arrays rather than large power
hungry I/O buffers.

Further benefits of an integrated secondary are
flexibility in the cache organization and management
policies that are not practical with an external cache.
Two previously mentioned examples are the 4-way
associativity and write-back cache protocol.

A third management policy for which integration
affords flexibility is cache hierarchy management.
With multiple levels of cache, it is necessary to specify
a policy for dealing with cases where two cache lines
at level n of the hierarchy would, if possible, be
sharing an entry in level n+1 of the hierarchy. The
policy followed by the ACT 7000SC is motivated by
the desire to get maximum cache utility and results in
the ACT 7000SC allowing entries in the primaries
which do not necessarily have a corresponding entry
in the secondary; the ACT 7000SC does not force the
primaries to be a subset of the secondary. For
example, if primary cache line A is being filled and a
cache line already exists in the secondary for primary
cache line B at the location where primary A’s line
would reside then that secondary entry will be
replaced by an entry corresponding to primary cache
line A and no action will occur in the primary for cache
line B. This operation will create the aforementioned
scenario where the primary cache line which initially
had a corresponding secondary entry will no longer
have such an entry. Such a primary line is called an
orphan. In general, cache lines at level n+1 of the
hierarchy are called parents of level n’s children.

Another ACT 7000SC cache management
optimization occurs for the case of a secondary cache
line replacement where the secondary line is dirty and
has a corresponding dirty line in the primary. In this
case, since it is permissible to leave the dirty line in
the primary, it is not necessary to write the secondary
line back to main memory. Taking this scenario one
step further, a final optimization occurs when the
aforementioned dirty primary line is replaced by
another line and must be written back, in this case, it
will be written directly to memory bypassing the
secondary cache.

Secondary Caching Protocols

Unlike the primary data cache, the secondary
cache supports only uncached and block write-back.
As noted earlier, cache lines managed with either of
the write-through protocols will not be placed in the
secondary cache. A new caching attribute, write-back
with secondary bypass, allows the secondary to be
bypassed entirely. When this attribute is selected, the
secondarywill not be filled on load misses and will not
be written on dirty write-backs from the primary.

9

Table 6 – Cache Attributes

Attribute Instruction Data Secondary

Size 16KB 16KB 256KB

Associativity 4-way 4-way 4-way

Replacement Algorithm. cyclic cyclic cyclic

Line size 32 byte 32 byte 32 byte

vAddr

pAddr

11..0

35..12

Index

Ta g

Write policy n.a. write-back, write-through block write-back, bypass

read policy n.a. non-blocking (2 outstanding) non-blocking (data only, 2

read order critical word first critical word first critical word first

write order NA sequential sequential

miss restart following: complete line first double (if waiting for

Parity per word per byte per doubleword

Cache Locking

The ACT 7000SC allows critical code or data
fragments to be locked into the primary and
secondary caches. The user has complete control
over what locking is performed with cache line
granularity. For instruction and data fragments in the
primaries, locking is accomplished by setting either or
both of the cache lock enable bits in the CP0 ECC
register, specifying the set via a field in the CP0 ECC
register, and then executing either a load instruction
or a Fill_I cache operation for data or instructions

vAddr

11..0

pAddr

35..12

data)

pAddr

15..0

pAddr

35..16

outstanding)

n.a.

movement operations in the embedded environment,
the ACT 7000SC significantly improves the speed of
operation of certain critical cache management
operations as compared with the R5000 and R4000
families. In particular, the speed of the
Hit-Write-back-Invalidate and Hit-Invalidate cache
operations has been improved in some cases by an
order of magnitude over that of the earlier families.
Table 8 compares the ACT 7000SC with the R4000
and R5000 processors.

Table 8 – Penalty Cycle

respectively. Only two sets are lockable within each
cache: set A and set B. Locking within the secondary
works identically to the primaries using a separate
secondary lock enable bit and the same set selection
field. As with the primaries, only two sets are lockable:
sets A and B. Table 7 summarizes the cache locking
capabilities.

Table 7 – Cache Locking Control

Operation Condition

Hit-Writebac
k-Invalidate

Miss 0 7

Hit-Clean 3 12

ACT 7000SCR4000/R500

Penalty

0

Cache

Primary I ECC[27] ECC[28]=0

Primary D ECC[26] ECC[28]=0

Secondary ECC[25] ECC[28]=0

Lock

Enable

Set Select Activate

ECC[28]=1

ECC[28]=1

ECC[28]=1

→
→

→
→

→
→

A
B

A
B

A
B

Fill_I

Load/Store

Fill_I or
Load/Store

Hit-Invalidate Miss 0 7

For the Hit-Dirty case of Hit-Writeback-Invalidate, if
the writeback buffer is full from some previous cache
eviction then n is the number of cycles required to
empty the write-back buffer. If the buffer is empty then

Hit-Dirty 3+n 14+n

Hit 2 9

n is zero.

Cache Management

To improve the performance of critical data

Aeroflex Circuit Technology SCD7000SC REV B 7/30/01 Plainview NY [phone]

The penalty value is the number of processor
cycles beyond the one cycle required to issue the
instruction that is required to implement the operation.

10

Primary Write Buffer

Writes to secondary cache or external memory,
whether cache miss write-backs or stores to
uncached or write-through addresses, use the
integrated primary write buffer. The write buffer holds
up to four 64-bit address and data pairs. The entire
buffer is used for a data cache write-back and allows
the processor to proceed in parallel with memory
update. For uncached and write-through stores, the
write buffer significantly increases performance by
decoupling the SysAD bus transfers from the
instruction execution stream.

System Interface

The ACT 7000SC provides a high-performance
64-bit system interface which is compatible with the
RM5200 Family and R5000. Unlike the R4000 and
R5000 family processors which provide only an
integral multiplication factor between SysClock and
the pipeline clock, the ACT 7000SC also allows
half-integral multipliers, thereby providing greater
granularity in the designers choice of pipeline and
system interface frequencies.

The interface consists of a 64-bit Address/Data bus
with 8 check bits and a 9-bit command bus. In
addition, there are six handshake signals and six
interrupt inputs. The interface has a simple timing
specification and is capable of transferring data
between the processor and memory at a peak rate of
600 MB/sec with a 75 MHz SysClock.

Figure 6 shows a typical embedded system using
the ACT 7000SC. This example shows a system with
a bank of DRAMs, and an interface ASIC which
provides DRAM control as well as an I/O port.

System Address/Data Bus

The 64-bit System Address Data (SysAD) bus is
used to transfer addresses and data between the
ACT 7000SC and the rest of the system. It is
protected with an 8-bit parity check bus, SysADC.

The system interface is configurable to allow easy
interfacing to memory and I/O systems of varying
frequencies. The data rate and the bus frequency at
which the ACT 7000SC transmits data to the system
interface are programmable via boot time mode
control bits. Also, the rate at which the processor
receives data is fully controlled by the external device.
Therefore, either a low cost interface requiring no
read or write buffering or a faster, high-performance
interface can be designed to communicate with the
ACT 7000SC. Again, the system designer has the
flexibility to make these price/performance trade-offs.

System Command Bus

The ACT 7000SC interface has a 9-bit System
Command (SysCmd) bus. The command bus
indicates whether the SysAD bus carries an address
or data. If the SysAD bus carries an address, then the
SysCmd bus also indicates what type of transaction is
to take place (for example, a read or write). If the
SysAD bus carries data, then the SysCmd bus also
gives information about the data (for example, this is
the last data word transmitted, or the data contains an
error). The SysCmd bus is bidirectional to support
both processor requests and external requests to the
ACT 7000SC. Processor requests are initiated by the
ACT 7000SC and responded to by an external
device. External requests are issued by an external
device and require the ACT 7000SC to respond.

The ACT 7000SC supports one to eight byte and
32-byte block transfers on the SysAD bus. In the case
of a sub-double-word transfer, the 3 low-order
address bits give the byte address of the transfer, and
the SysCmd bus indicates the number of bytes being
transferred.

Handshake Signals

There are six handshake signals on the system
interface. Two of these, RdRdy* and WrRdy*, are
used by an external device to indicate to the ACT
7000SC whether it can accept a new read or write

8

Memory I/O

Controller

Address

Control

XX

PCI Bus

ACT 7000SC

DRAM

72

Latch

72

SysCmd

Flash /

Boot

ROM

SysAD Bus

72

25

Figure 6 – Typical Embedded System Block Diagram

Aeroflex Circuit Technology SCD7000SC REV B 7/30/01 Plainview NY [phone]

11

transaction. The ACT 7000SC samples these signals
before deasserting the address on read and write
requests.

ExtRqst* and Release* are used to transfer control
of the SysAD and SysCmd buses from the processor
to an external device. When an external device needs
to control the interface, it asserts ExtRqst*. The ACT
7000SC responds by asserting Release* to release
the system interface to slave state.

ValidOut* and ValidIn* are used by the ACT
7000SC and the external device respectively to
indicate that there is a valid command or data on the
SysAD and SysCmd buses. The ACT 7000SC
asserts ValidOut* when it is driving these buses with
a valid command or data, and the external device
drives ValidIn* when it has control of the buses and is
driving a valid command or data.

System Interface Operation

The ACT 7000SC can issue read and write
requests to an external device, while an external
device can issue null and write requests to the ACT
7000SC.

For processor reads, the ACT 7000SC asserts
ValidOut* and simultaneously drives the address and
read command on the SysAD and SysCmd buses. If
the system interface has RdRdy* asserted, then the
processor tristates its drivers and releases the system
interface to slave state by asserting Release*. The
external device can then begin sending data to the
ACT 7000SC.

Figure 7 shows a processor block read request and
the external agent read response for a system with a
transaction.

The read latency is 4 cycles (ValidOut* to
ValidIn*), and the response data pattern is DDxxDD.
Figure 9 shows a processor block write where the
processor was programmed with write-back data rate
boot code 2, or DDxxD-Dxx.

Data Prefetch

The ACT 7000SC is the first Aeroflex design to

support the MIPS IV integer data prefetch (PREF) and
floating-point data prefetch (PREFX) instructions.
These instructions are used by the compiler or by an
assembly language programmer when it is known or
suspected that an upcoming data reference is going
to miss in the cache. By appropriately placing a
prefetch instruction, the memory latency can be
hidden under the execution of other instructions. If the
execution of a prefetch instruction would cause a
memory management or address error exception the
prefetch is treated as a NOP.

The “Hint” field of the data prefetch instruction is
used to specify the action taken by the instruction.
The instruction can operate normally (that is, fetching
data as if for a load operation) or it can allocate and fill
a cache line with zeroes on a primary data cache
miss.

Enhanced Write Modes

The ACT 7000SC implements two enhancements
to the original R4000 write mechanism: Write Reissue
and Pipeline Writes. In write reissue mode, a write
rate of one write every two bus cycles can be
achieved. A write issues if WrRdy* is asserted two
cycles earlier and is still asserted during the issue
cycle. If it is not still asserted then the last write will
reissue. Pipe-lined writes have the same two bus
cycle write repeat rate, but can issue one additional
write following the deassertion of WrRdy*.

External Requests

The ACT 7000SC can respond to certain requests
issued by an external device. These requests take
one of two forms: Write requests and Null requests.
An external device executes a write request when it
wishes to update one of the processors writable
resources such as the internal interrupt register. A null
request is executed when the external device wishes
the processor to reassert ownership of the processor
external interface. Typically a null request will be
executed after an external device, that has acquired
control of the processor interface via ExtRqst*, has

SysClock

SysAD

SysCmd

ValidOut*

ValidIn*

RdRdy*

WrRdy*

Release*

Addr

Read

Data0

nData

Data1

nData

Data2 Data3

nData NEOD

Figure 7 – Processor Block Read

Aeroflex Circuit Technology SCD7000SC REV B 7/30/01 Plainview NY [phone]

12

SysClock

SysAD

SysCmd

ValidOut*

ValidIn*

RdRdy*

WrRdy*

Release*

Data0 Data1Addr

NData NDataWrite NData NEODNData

Figure 8 – Processor Block Write

completed an independent transaction between itself
and system memory in a system where memory is
connected directly to the SysAD bus. Normally this
transaction would be a DMA read or write from the I/O
system.

Test / Breakpoint Registers

To increase both observability and controllability of
the processor thereby easing hardware and software
debugging, a pair of Test/Break-point, or Watch,
registers, Watch1 and Watch2, have been added to
the ACT 7000SC. Each Watch register can be
separately enabled to watch for a load address, a
store address, or an instruction address. All address
comparisons are done on physical addresses. An
associated register, Watch Mask, has also been
added so that either or both of the Watch registers
can compare against an address range rather than a
specific address. The range granularity is limited to a
power of two.

When enabled, a match of either Watch register
results in an exception. If the Watch is enabled for a
load or store address then the exception is the Watch
exception as defined for the R4000 with Cause
exception code twenty-three. If the Watch is enabled
for instruction addresses then a newly defined
Instruction Watch exception is taken and the Cause
code is sixteen. The Watch register which caused the
exception is indicated by Cause bits 25..24.

Table 9 summarizes a Watch operation.

Data2 Data3

Performance Counters

Like the Test/Break-point capability described
above, the Performance Counter feature has been
added to improve the observability and controllability
of the processor thereby easing system debug and,
especially in the case of the performance counters,
easing system tuning.

The Performance Counter feature is implemented
using two new CP0 registers, PerfCount and
PerfControl. The PerfCount register is a 32-bit
writable counter which causes an interrupt when bit
31 is set. The PerfControl register is a 32-bit register
containing a five bit field which selects one of
twenty-two event types as well as a handful of bits
which control the overall counting function. Note that
only one event type can be counted at a time and that
counting can occur for user code, kernel code, or
both. The event types and control bits are listed in
Table 10.

Table 9 – Watch Control Register

Register Bit Field/Function

63 62 61 60:36 35:2 1:0

Watch1, 2 Store Load Instr 0 Addr 0

31:2 1 0

Watch
Mask

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Mask Mask

Watch

Mask

Watch

2

1

13

Table 10 – Performance Counter Control

The performance counter interrupt will only occur
when interrupts are enabled in the Status register,

PerfControl

Field

4..0 Event Type
00: Clock cycles
01: Total instructions issued
02: Floating-point instructions issued
03: Integer instructions issued
04: Load instructions issued
05: Store instructions issued
06: Dual issued pairs
07: Branch prefetches
08: External Cache Misses
09: Stall cycles
0A: Secondary cache misses
0B: Instruction cache misses
0C: Data cache misses
0D: Data TLB misses
0E: Instruction TLB misses
0F: Joint TLB instruction misses
10: Joint TLB data misses
11: Branches taken
12: Branches issued
13: Secondary cache writebacks
14: Primary cache writebacks
15: Dcache miss stall cycles (cycles

where both cache miss tokens
taken and a third address is

requested)
16: Cache misses
17: FP possible exception cycles
18: Slip Cycles due to multiplier busy
19: Coprocessor 0 slip cycles
1A: Slip cycles due to pending

non-blockingloads
1B: Write buffer full stall cycles
1C: Cache instruction stall cycles
1D: Multiplier stall cycles
1E: Stall cycles due to pending

non-blocking loads - stall start of

exception

7..5 Reserved (must be zero)
8 Count in Kernel Mode

0: Disable
1: Enable

9 Count in User Mode

0: Disable
1: Enable

10 Count Enable

0: Disable
1: Enable

31..11 Reserved (must be zero)

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Description

IE=1, and Interrupt Mask bit 13 (IM[13]) of the
coprocessor 0 interrupt control register is not set.

Since the performance counter can be set up to
count clock cycles, it can be used as either a) a
second timer or b) a watchdog interrupt. A watchdog
interrupt can be used as an aid in debugging system
or software “hangs.” Typically the software is setup to
periodically update the count so that no interrupt will
occur. When a hang occurs the interrupt ultimately
triggers thereby breaking free from the hang-up.

Interrupt Handling

In order to provide better real time interrupt
handling, the ACT 7000SC provides an extended set
of hardware interrupts each of which can be
separately prioritized and separately vectored.

As described above, the performance counter is
also a hardware interrupt source, IP[13]. Also,
whereas the R4000 and R5000 family processors
map the timer interrupt onto IP[7], the ACT 7000SC
provides a separate interrupt, IP[12], for this purpose.

All of these interrupts, IP[13..0], the Performance
Counter, and the Timer, have corresponding interrupt
mask bits, IM[13..0], and interrupt pending bits,
IP[13..0], in the Status, Interrupt Control, and Cause
registers. The bit assignments for the Interrupt
Control and Cause registers are shown in Table 11
and Table 12 below. The Status register has not
changed from the RM5200 Family and R5000, and is
not shown.

The IV bit in the Cause register is the global enable
bit for the enhanced interrupt features. If this bit is
clear then interrupt operation is compatible with the
RM5200 Family and R5000. Although not related to
the interrupt mechanism, note that the W1 and W2
bits indicate which Watch register caused a particular
Watch exception.

In the Interrupt Control register, the interrupt vector
spacing is controlled by the Spacing field as
described below. The Interrupt Mask field (IM[15..8])
contains the interrupt mask for interrupts eight
through thirteen. IM[15..14] are reserved for future
use. The Timer Exclusive (TE) bit if set moves the
Timer interrupt to IP[12]. If clear, the Timer interrupt
will be or’ed into IP[7] as on the R5000.

The Interrupt Control register uses IM13 to enable
the Performance Counter Control.

Priority of the interrupts is set via two new
coprocessor 0 registers called Interrupt Priority Level
Lo, IPLLO, and Interrupt Priority Level Hi, IPLHI.

These two registers contain a four-bit field
corresponding to each interrupt thereby allowing each
interrupt to be programmed with a priority level from 0
to 13 inclusive. The priorities can be set in any
manner including having all the priorities set exactly
the same. Priority 0 is the highest level and priority 15
the lowest. The format of the priority level registers is
shown in Table 13 and Table 14 below. The priority

14

Table 11 – Cause Register

31 30 29,28 27 26 25 24 23..8 7 6..2 0,1

BD 0 CE 0 W2 W1 IV IP[15..0] 0 EXC 0

Table 12 – Interupt Control Register

31..16 15..8 7 6..5 4..00

0 IM[15..8] TE 0 Spacing

Table 13 – IPLLO Register

31..28 27..24 23..20 19..16 15..12 11..8 7..4 3..0

IPL7 IIPL6 IPL5 IPL4 IPL3 IPL2 IPL1 IPL0

Table 14 – IPLHI Register

31..28 27..24 23..20 19..16 15..12 11..8 7..4 3..0

0 0 IPL13 IPL12 IPL11 IPL10 IPL9 IPL8

level registers are located in the coprocessor 0 control
register space. For further details about the control
space see the section describing coprocessor 0.

In addition to programmable priority levels, the ACT
7000SC also permits the spacing between interrupt
vectors to be programmed. For example, the
minimum spacing between two adjacent vectors is
0x20 while the maximum is 0x200. This
programmability allows the user to either set up the
vectors as jumps to the actual interrupt routines or, if
interrupt latency is paramount, to include the entire
interrupt routine at the vector. Table 15 illustrates the
complete set of vector spacing selections along with
the coding as required in the Interrupt Control register
bits 4:0.

In general, the active interrupt priority combined
with the spacing setting generates a vector offset
which is then added to the interrupt base address of
0x200 to generate the interrupt exception offset. This
offset is then added to the exception base to produce
the final interrupt vector address.

Table 15 – Interrupt Vector Spacing

Standby Mode

The ACT 7000SC provides a means to reduce the
amount of power consumed by the internal core when
the CPU would not otherwise be performing any
useful operations. This state is known as Standby
Mode.

Executing the WAIT instruction enables interrupts
and enters Standby Mode. When the WAIT instruction
completes the W pipe stage, if the SysAD bus is
currently idle, the internal processor clocks will stop
thereby freezing the pipeline. The phase lock loop, or
PLL, internal timer/ counter, and the “wake up” input
pins: IP[5:0]*, NMI*, ExtReq*, Reset*, and
ColdReset* continue to operate in their normal
fashion. If the SysAD bus is not idle when the WAIT
instruction completes the W pipe stage, then the
WAIT is treated as a NOP. Once the processor is in
Standby, any interrupt, including the internally
generated timer interrupt, will cause the processor to
exit Standby and resume operation where it left off.
The WAIT instruction is typically inserted in the idle
loop of the operating system or real time executive.

JTAG Interface

ICR[4..0] Spacing

0x0 0x000

0x1 0x020

0x2 0x040

0x4 0x080

0x8 0x100

0x10 0x200

others reserved

Aeroflex Circuit Technology SCD7000SC REV B 7/30/01 Plainview NY [phone]

The ACT 7000SC interface supports JTAG
boundary scan in conformance with IEEE 1149.1. The
JTAG interface is especially helpful for checking the
integrity of the processor’s pin connections.

Boot-Time Options

Fundamental operational modes for the processor
are initialized by the boot-time mode control interface.
The boot-time mode control interface is a serial
interface operating at a very low frequency
(SysClock divided by 256). The low frequency
operation allows the initialization information to be

15

kept in a low cost EPROM; alternatively the twenty or
so bits could be generated by the system interface
ASIC.

Immediately after the VccOK signal is asserted, the
processor reads a serial bit stream of 256 bits to
initialize all the fundamental operational modes.

ModeClock runs continuously from the assertion of
VccOK.

Boot-Time Modes

The boot-time serial mode stream is defined in
Table 16. Bit 0 is the bit presented to the processor
when VccOK is deasserted; bit 255 is the last.

Table 16 – Boot Time Mode Stream (Cont.)

Mode bit Description

10..9 Non-Block Write Control

00: R4000 compatible non-block writes

01: Reserved

10: pipelined non-block writes

11: non-block write re-issue

11 Timer Interrupt Enable/Disable

Table 16 – Boot Time Mode Stream

Mode bit Description

0 Reserved: Must be zero

4..1 Write-back data rate

0: DDDD

1: DDxDDx

2: DDxxDDxx

3: DxDxDxDx

4: DDxxxDDxxx

5 DDxxxxDDxxxx

6: DxxDxxDxxDxx

7: DDxxxxxxDDxxxxxx

8: DxxxDxxxDxxxDxxx

9-15:Reserved

7..5 SysClock to Pclock Multiplier
Mode bit 20 = 0 / Mode bit 20 = 1

0: Multiply by 2/x

1: Multiply by 3/x

2: Multiply by 4/x

3: Multiply by 5/2.5

4: Multiply by 6/x

5: Multiply by 7/3.5

6: Multiply by 8/x

7: Multiply by 9/4.5

8 Specifies byte ordering. Logically ORed

with BigEndian input signal.

0: Enable the timer interrupt on IP[5]

1: Disable the timer interrupt on IP[5]

12 Reserved: Must be zero

14..13 Output driver strength - 100% = fastest

00: 67% strength

01: 50% strength

10: 100% strength

11: 83% strength

15 Reserved must be zero

17..16 System configuration identifiers ­software visible in processor
Config[21..20] register

19..18 Reserved: Must be zero

20 Pclock to SysClock multipliers.

0: Integer multipliers (2,3,4,5,6,7,8,9)

1: Half integer multipliers (2.5,3.5,4.5)

21 External Bus Width.

0: 64-bit

1: 32-bit

23..22 Reserved: Must be zero

24 JTLB Size.

0: 48 dual-entry

1: 64 dual-entry

25 On-chip secondary cache control.

0: Disable

1: Enable

255..26 Reserved: Must be zero

0: Little endian

1: Big endian

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PLL Analog Power Filtering

The ACT 7000SC includes extra PLL Analog Power Fiiltering circuitry designed to provide low noise,
temperature stable filtering for the VccP and VssP signals. The included circuitry consists of several passive
components located at the closest possible point to the RM7000 die and is configured as shown in Figure 9.

5 Ω

VccP

64

RM7000

Die

VssP

65

5 Ω

.01

µF

1000

pF

Figure 9 – ACT 7000SC Including PLL Filter Circuit

Additional board level PPL filtering is also required. The recommended configuration is shown in
Figure 10.

5 Ω

VccInt

64

VccP

10
µF

5 Ω

VssInt

.1

µF

1000

pF

65

VssP

Figure 10 – Recommended Board Level PLL Filter circuit

for the ACT 7000SC

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Absolute Maximum Rating

1

Symbol Parameter Limits Units

V

TERM

T

C

T

STG

I

IN

I

OUT

Note 1: Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating

only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is
not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.

IN

Note 2: V

Note 3: When V

Note 4: Not more than one output should be shorted at a time. Duration of the short should not exceed 30 seconds.

minimum = -2.0V for pulse width less than 15ns. VIN should not exceed 3.9 Volts.

IN

Terminal Voltage with respect to V

SS

-0.52 to +3.9 V

Case Operating Temperature -55 to +125 °C

Storage Temperature -65 to +150 °C

DC Input Current 20

DC Output Current

< 0V or VIN > VCCIO

4

3

50 mA

mA

Recommended Operating Conditions

CPU Speed Temperature Vss VssInt VccIO VccP

150 - 225 MHz -55°C to +125°C (TC) 0V 2.5V ±5% 3.3V ±5% 2.5V ±5%

Note: VCC I/O should not exceed VccInt by greater than 1.2V during the power- up sequence.

Note: Applying a logic high state to any I/O pin before VccInt becomes stable is not recommended.

Note: As specified in IEEE 1149.1 (JTAG), the JTMS pin must be held low during reset to avoid entering JTAG test mode. Refer to the RM7000 Family

Users Manual, Appendix E.

DC Electrical Characteristics

Parameter Minimum Maximum Conditions

V

OL

V

OH

V

OL

V

OH

V

IL

V

IH

I

IN

C

IN

VCCIO - 0.1V

2.4V

-0.5V 0.2 xVCCIO

0.7 x VCCIO VCCIO + 0.5V

0.1V |I

0.4V |I

±20µA
±20µA

10pF

|= 20µA

OUT

|= 4mA

OUT

VIN=0
VIN=VCCIO

C

OUT

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10pF

Power Consumption

CPU Clock Speed

Parameter Condition

VccInt
Power

(mWatts)

Note 1: Typical integer instruction mix and cache miss rates with worst case supply voltage.

Note 2: Worst case instruction mix with worst case supply voltage.

Note: I/O supply power is application dependant, but typically <10% of VccInt.

Standby No SysAD bus activity 500 1000 1500 2000

Active R4000 write protocol with no

FPU operation
(integer Instruction only)

Write re-issue or pipelined
writes with superscalar
(integer and floating point
instructions)

150 MHz 200 MHz 210 MHz 225 MHz

1

Typ

2200 4400 2700 5400 2800 5600 3800 7600

2550 5100 3150 6300 3300 6600 4250 8500

Max2Typ1Max2Typ1Max2Typ1Max

AC Electrical Characteristics – Clock Parameters

Parameter Symbol

Tes t

Condition

2

CPU Clock Speed

Units150 MHz 200 MHz 210 MHz 225 MHz

Min Max Min Max Min Max Min Max

SysClock High

SysClock Low

SysClock Frequency 25 75 25 75 25 70 25 75 MHz

SysClock Period

Clock Jitter for SysClock

SysClock Rise Time

SysClock Fall Time

ModeClock Period

JTAG Clock Period

Note: Operation of the ACT 7000 is only guaranteed with the Phase Lock Loop enabled

tSCHIGH

t

SCLOW

tSCP

t

JITTERIN

t

SCRISE

tSCFALL

t

MODECKP

t

JTAGCKP

Transition < 5ns3333ns

Transition < 5ns3333ns

40 40 40 40 ns

±200 ±200 ±150 ±150 ps

2222ns

2222ns

256 256 256 256

4444

t

SCP

t

SCP

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System Interface Parameters

Parameter

8

Sym Test Conditions

150MHz 200MHz 210MHz 225MHz

Min Max Min Max Min Max Min Max

Data Output

Data Setup

Data Hold

Notes:

1. Timings are measured from 1.5V of the clock to 1.5V of the signal.

2. Capacitive load for all output timings is 50pF.

3. Data Output timing applies to all signal pins whether tristate I/O or output only.

4. Setup and Hold parameters apply to all signal pins whether tristate I/O or input only.

2,3

4

4

t

t

t

DO

DS

DH

mode

mode

mode

mode

t

rise

t

fall

= 10 (fastest)

14...13

= 11

14...13

= 00

14...13

= 01 (slowest)

14...13

= see above table

= see above table

1.0 6.0 1.0 6.0 1.0 5.5 1.0 5.5 ns

1.0 6.5 1.0 6.5 1.0 6.0 1.0 6.0 ns

1.0 7.0 1.0 7.0 1.0 6.5 1.0 6.5 ns

1.0 7.5 1.0 7.5 1.0 7.0 1.0 7.0 ns

2.52.52.52.5 ns

1.01.01.01.0 ns

Boot-Time Interface Parameters

Parameter Symbol Test Cond itions Min Max Units

Mode Data Setup

t

DS

4 SysClock cycles

Units

Mode Data Hold

t

DH

Clock Timing

SysClock

t

SCRis etSCFall

System Interface Timing

SysClock

Data

SysClock

Data

0 SysClock cycles

t

SCP

±t

JitterIn

SysClock Timing

(SysAD, SysCmd, ValidIn*, ValidOut*, etc.)

t

DS

t

DH

Data

Input Timing

t

DO

t

DO

MIN

Data Data

Output Timing

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20

Pin Descriptions

The following is a list of control, data, clock, interrupt, and miscellaneous pins of the ACT 7000SC.

Pin Name Type Description

System interface:

ExtRqst* Input External request

Signals that the system interface is submitting an external request.

Release* Output Release interface

Signals that the processor is releasing the system interface to slave state

RdRdy* Input Read Ready

Signals that an external agent can now accept a processor read.

WrRdy* Input Write Ready

Signals that an external agent can now accept a processor write request.

ValidIn* Input Valid Input

Signals that an external agent is now driving a valid address or data on the
SysAD bus and a valid command or data identifier on the SysCmd bus.

ValidOut* Output Valid output

Signals that the processor is now driving a valid address or data on the SysAD
bus and a valid command or data identifier on the SysCmd bus.

SysAD(63:0) Input/

Output

System address/data bus
A 64-bit address and data bus for communication between the processor and an
external agent.

SysADC(7:0) Input/

Output

SysCmd(8:0) Input/

Output

System address/data check bus
An 8-bit bus containing parity check bits for the SysAD bus during data cycles.

System command/data identifier bus
A 9-bit bus for command and data identifier transmission between the processor
and an external agent.

SysCmdP Input/

Output

System Command/Data Identifier Bus Parity
For the RM7000, unused on input and zero on output.

Clock/Control interface:

SysClock Input System clock

Master clock input used as the system interface reference clock. All output
timings are relative to this input clock. Pipeline operation frequency is derived by
multiplying this clock up by the factor selected during boot initialization

VccP Input Vcc for PLL

Quiet VccInt for the internal phase locked loop. Must be connected to VccInt.
See Figure 10 for additional PPL filtering information.

VssP Input Vss for PLL

Quiet Vss for the internal phase locked loop. Must be connected to Vss.
See Figure 10 for additional PPL filtering information.

Interrupt Interface

Int*(5:0) Input Interrupt

Six general processor interrupts, bit-wise ORed with bits 5:0 of the interrupt
register.

NMI* Input Non-maskable interrupt

Non-maskable interrupt, ORed with bit 15 of the interrupt register (bit 7 in R5000
compatibility mode).

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Pin Descriptions (Cont.)

The following is a list of control, data, clock, interrupt, and miscellaneous pins of the ACT 7000SC.

Pin Name Type Description

JTAG interface:

JTDI Input JTAG data in

JTCK Input JTAG clock input

JTDO Output JTAG data out

JTMS Input JTAG command

Initialization Interface:

BigEndian Input Big Endian / Little Endian Control

VccOK Input Vcc is OK

ColdReset* Input Cold Reset

Reset* Input Reset

JTAG serial data in.

JTAG serial clock input.

JTAG serial data out.

JTAG command signal, signals that the incoming serial data is command data.

Allows the system to change the processor addressing mode without rewriting
the mode ROM.

When asserted, this signal indicates to the ACT 7000 that the 2.5V power supply
has been above 2.25V for more than 100 milliseconds and will remain stable.
The assertion of VccOK initiates the reading of the boot-time mode control serial
stream.

This signal must be asserted for a power on reset or a cold reset. ColdReset
must be de-asserted synchronously with SysClock.

This signal must be asserted for any reset sequence. It may be asserted
synchronously or asynchronously for a cold reset, or synchronously to initiate a
warm reset. Reset must be de-asserted synchronously with SysClock.

ModeClock Output Boot Mode Clock

Serial boot-mode data clock output at the system clock frequency divided by two
hundred and fifty six.

ModeIn Input Boot Mode Data In

Serial boot-mode data input.

For additional Detail Information regarding the operation of the Quantum Effect Devices (QED) RISCMark
RM7000, 64-Bit Superscalar Microprocessor see the latest QED datasheet and users guide
(www.qedinc.com).

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22

Package Information – "F17" – CQFP 208 Leads

1.131 (28.727) SQ

1.109 (28.169) SQ

10453

52

105

.0236 (.51)

1.009 (25.63)
.9998 (25.37)

51 Spaces at .0197

(51 Spaces at .50)

Pin 1 Chamfer

Detail "A"

.005 (.127)

.0158 (.49)

.010R REF

.010R REF

0°±5°

.100 (2.540)
.080 (2.032)

.015 (.381)
.009 (.229)

.035 (.889)
.025 (.635)

Detail "A"

.008 (.202)

1

208

.960 (24.384) SQ

REF

1.331 (33.807)

1.269 (32.233)

Note: Pin rotation is opposite of QEDs PQUAD due to cavity-up construction.

156

157

.055 (1.397)

REF

.055 (1.397)
.045 (1.143)

.115 (2.921)

MAX

Package Information – "F24" – Inverted CQFP 208 Leads

1.131 (28.727) SQ

1.109 (28.169) SQ

105156

157

104

Lid

.130 (3.302)

MAX

.010 (.253)
.007 (.178)

Units: Inches (Millimeters)

.055 (1.397)
.045 (1.143)

.115 (2.921)

MAX

.0236 (.51)

1.009 (25.63)
.9998 (25.37)

51 Spaces at .0197

(51 Spaces at .50)

Pin 1 Chamfer

Detail "A"

.0158 (.49)

208

.012R REF

.012R REF

.055 (1.397)

0°±5°

.100 (2.540)
.080 (2.032)

53

1

52

.139 (3.531)

MAX

Lid

.060 (1.524)
.040 (1.016)

Detail "A"

REF

.010 (.253)
.007 (.178)

Units: Inches (Millimeters)

.960 (24.384) REF

1.331 (33.807)

.005 (.127)

.008 (.202)

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Note: Pin rotation is Identical to QEDs PQUAD due to cavity-down construction.

1.291 (32.791)

23

.024 (.610)
.010 (.253)

ACT 7000SC Microprocessor CQFP Pinouts – "F17" & "F24"

Pin # Function Pin # Function Pin # Function Pin # Function

1 VccIO 53 NC 105 VccIO 157 NC
2 NC 54 NC 106 NMI* 158 NC
3 NC 55 NC 107 ExtRqst* 159 NC
4 VccIO 56 VccIO 108 Reset* 160 NC
5 Vss 57 Vss 109 ColdReset* 161 VccIO
6 SysAD4 58 ModeIn 110 VccOK 162 Vss
7 SysAD36 59 RdRdy* 111 BigEndian 163 SysAD28
8 SysAD5 60 WrRdy* 112 VccIO 164 SysAD60

9 SysAD37 61 ValidIn* 113 Vss 165 SysAD29
10 VccInt 62 ValidOut* 114 SysAD16 166 SysAD61
11 Vss 63 Release* 115 SysAD48 167 VccInt
12 SysAD6 64 VccP 116 VccInt 168 Vss
13 SysAD38 65 VssP 117 Vss 169 SysAD30
14 VccIO 66 SysClock 118 SysAD17 170 SysAD62
15 Vss 67 VccInt 119 SysAD49 171 VccIO
16 SysAD7 68 Vss 120 SysAD18 172 Vss
17 SysAD39 69 VccIO 121 SysAD50 173 SysAD31
18 SysAD8 70 Vss 122 VccIO 174 SysAD63
19 SysAD40 71 VccInt 123 Vss 175 SysADC2
20 VccInt 72 Vss 124 SysAD19 176 SysADC6
21 Vss 73 SysCmd0 125 SysAD51 177 VccInt
22 SysAD9 74 SysCmd1 126 VccInt 178 Vss
23 SysAD41 75 SysCmd2 127 Vss 179 SysADC3
24 VccIO 76 SysCmd3 128 SysAD20 180 SysADC7
25 Vss 77 VccIO 129 SysAD52 181 VccIO
26 SysAD10 78 Vss 130 SysAD21 182 Vss
27 SysAD42 79 SysCmd4 131 SysAD53 183 SysADC0
28 SysAD11 80 SysCmd5 132 VccIO 184 SysADC4
29 SysAD43 81 VccIO 133 Vss 185 VccInt
30 VccInt 82 Vss 134 SysAD22 186 Vss
31 Vss 83 SysCmd6 135 SysAD54 187 SysADC1
32 SysAD12 84 SysCmd7 136 VccInt 188 SysADC5
33 SysAD44 85 SysCmd8 137 Vss 189 SysAD0
34 VccIO 86 SysCmdP 138 SysAD23 190 SysAD32
35 Vss 87 VccInt 139 SysAD55 191 VccIO
36 SysAD13 88 Vss 140 SysAD24 192 Vss
37 SysAD45 89 VccInt 141 SysAD56 193 SysAD1
38 SysAD14 90 Vss 142 VccIO 194 SysAD33
39 SysAD46 91 VccIO 143 Vss 195 VccInt
40 VccInt 92 Vss 144 SysAD25 196 Vss
41 Vss 93 Int0* 145 SysAD57 197 SysAD2
42 SysAD15 94 Int1* 146 VccInt 198 SysAD34
43 SysAD47 95 Int2* 147 Vss 199 SysAD3
44 VccIO 96 Int3* 148 SysAD26 200 SysAD35
45 Vss 97 Int4* 149 SysAD58 201 VccIO
46 ModeClock 98 Int5* 150 SysAD27 202 Vss
47 JTDO 99 VccIO 151 SysAD59 203 NC
48 JTDI 100 Vss 152 VccIO 204 NC
49 JTCK 101 NC 153 Vss 205 NC
50 JTMS 102 NC 154 NC 206 NC
51 VccIO 103 NC 155 NC 207 VccIO
52 Vss 104 NC 156 Vss 208 Vss

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CIRCUIT TECHNOLOGY

Sample Ordering Information

Part Number Screening Speed (MHz) Package

ACT-7000SC-150F17I Industrial Temperature 150 208 Lead CQFP

ACT-7000SC-200F17C Commercial Temperature 200 208 Lead CQFP

ACT-7000SC-210F17T Military Temperature 210 208 Lead CQFP

ACT-7000SC-225F17M Military Screening 225 208 Lead CQFP

Part Number Breakdown

ACT– 7000 SC – 225 F17 M

Aeroflex Circuit
Technology

Base Processor Type

Cache Style

SC = Secondary Cache

Maximum Pipeline Freq.

150 = 150MHz
200 = 200MHz
210 = 210MHz
225 = 225MHz
240 = 240MHz (Future Option)
250 = 250MHz (Future Option)
266 = 266MHz (Future Option)

C = Commercial Temp, 0°C to +70°C
I = Industrial Temp, -40°C to +85°C
T = Military Temp, -55°C to +125°C
M = Military Temp, -55°C to +125°C, Screened
Q = MIL-PRF-38534 Compliant/SMD if applicable

F17 = 1.120" SQ 208 Lead CQFP
F24 = 1.120" SQ Inverted 208 Lead CQFP

Screened to the individual test methods of MIL-STD-883

*

Screening

Package Type & Size

Surface Mount Package

*

This document may, wholly or partially, be subject to change without notice. Aeroflex reserves the right to make changes to its products or specifications at any time
without notice.

Aeroflex will not be held responsible for any damage to the user or any property that may result from accidents, misuse, or any other causes arising during operation of
the user's unit.

Aeroflex does not assume any responsibility for use of any circuitry described other than the circuitry embodied in a Aeroflex product. The company makes no
representations that the circuitry described herein is free from patent infringement or other rights of third parties, which may result from its use. No license is granted by
implication or otherwise under any patent, patent rights, or other rights, of Aeroflex.

The QED logo and RIS CMark are trademarks of Quantum Effect Devices, Inc.

MIPS is a registered trademark of MIPS Technologies, Inc. All other trademarks are the respective property of the trademark holders.

Aeroflex Circuit Technology
35 South Service Road
Plainview New York 11803
www.aeroflex.com

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