4 of 21 June 20, 2000
79RC32364™
*Notice: The information in this document is subject to change without notice
This allows the system architect to allocate address space according to
the most efficient use of bus bandwidth. For example, stack data may be
accessed always as write-back, while packet data may be best
accessed as write through, for later DMA out to an I/O port.
The RC32364 cache controller works in conjunction with these
attributes, enabling an application to alias a region of physical memory
through multiple virtual spaces. The cache controller will also ensure
that regardless of which address space is used the current copy of data
will be provided when referenced, and it will further guarantee that the
cache is properly managed with respect to main memory.
Debug Support
Debug SupportDebug Support
Debug Support
To facilitate software debug, the RC32364 adds a pair of watch regis-
ters to CP0. When enabled, these registers will cause the CPU to take
an exception when a “watched” address is appropriately accessed.
In addition, the RC32364 implements an Enhanced JTAG interface,
which requires the inclusion of significant amounts of debug support
logic on-chip, facilitating the development of low-cost in-circuit emulation
equipment.
For low-cost In-Circuit Emulation, the RC32364 provides an
Enhanced JTAG interface. This interface consists of two modes of
operation: Run-Time Mode and Real-Time Mode.
The Run-Time Mode provides a standard JTAG interface for on-chip
debugging, and the Real-Time Mode provides additional status pins—
PCST[2:0]—which are used in conjunction with JTAG pins for Real-Time
Trace information at the processor internal clock or any division of the
pipeline clock.
The RC32364 implements the traditional RC4000 model of interrupt
processing. However, this model has been enhanced to benefit real-
time systems.
To speed interrupt exception decoding, the RC32364 adds a sepa-
rate interrupt vector. Unlike the RC3000 family—which utilizes a single
common exception vector for all exception types (including interrupts)—
the RC32364 allows kernel software to enable a separate interrupt
exception vector.
When enabled, this vector location speeds interrupt processing by
allowing software to avoid decoding interrupts from general purpose
exceptions.
Development Tools
Development ToolsDevelopment Tools
Development Tools
An array of tools facilitate rapid development of RC32364-based
systems, allowing a wide variety of customers to take advantage of the
processor’s high-performance capabilities while maintaining short time-
to-market goals.
The RC32364 incorporates an enhanced JTAG debug interface. This
interface uses a small number of pins, combined with on-chip debug
support logic, to enable the development of low-cost in-circuit emulators
for high-speed IDT processors.
Cache Memory
Cache MemoryCache Memory
Cache Memory
To keep the RC32364’s high-performance pipeline full and operating
efficiently, the RC32364 incorporates on-chip instruction and data
caches that can each be accessed in a single processor cycle. Each
cache has its own 32-bit data path and can be accessed in the same
pipeline clock cycle.
The RC32364 incorporates a two-way set associative on-chip
Instruction Cache. This virtually indexed, physically tagged cache is
8kB in size and parity protected. Because this cache is virtually indexed,
the virtual-to-physical address translation occurs in parallel with the
cache access. The tag holds a 21-bit physical address, a valid bit, lock
bit, a parity bit, and the FIFO replacement bit.
For fast, single cycle data access, the RC32364 includes a 2kB on-
chip data cache that is two-way set associative with a fixed 16-byte
(four words) line size. The data cache is protected with byte parity and
its tag is protected with a single parity bit. It is virtually indexed and
physically tagged to allow simultaneous address translation and data
cache access.
The RC32364 supports a cache-locking feature to critical sections
of code and data into on-chip caches, to guarantee fast accesses. The
implementation of cache-locking is on a “per-line” basis, enabling the
system designer to maximize the efficiency of the system cache.
Writes to external memory—whether cache miss write-backs or
stores to uncached or write-through addresses—use the on-chip write
buffer. The write buffer holds a maximum of four address and data
pairs. The entire buffer is used for a data cache writeback and allows
the processor to proceed in parallel with a memory update.
System interfaces
System interfacesSystem interfaces
System interfaces
The RC32364 supports a 32-bit system interface, allowing the CPU
to interface with a lower cost memory system. The main features of the
system interface include:
◆
Multiplexed address and data bus with Address Latch Enable
(ALE) signal to demultiplex the A/D bus.
◆
Support of variable port widths, including boot device.
◆
Support of multiple pipeline to system clock ratios, with the CPU
core frequency being derived from the input system clock.
◆
Incorporation of a DMA arbiter, allowing an external master
control of the external bus.
The 32-bit system address/data (A/D) bus is used to transfer
addresses and data between the RC32364 and the rest of the system.
The ALE signal is provided to demultiplex the address from this bus.
The DATAEN* signal indicates the data phase of the A/D bus and DT/R*
indicates the direction of data flow. BE*[3:0] indicates the valid bytes on
the bus. Additional ADDR[3:2] provides incremental address during
burst transfers.
To indicate system interface bus activity, the RC32364 provides a
cycle-in-progress (CIP*) signal. The RD* and WR* signals indicate the
type of cycle in progress. And to terminate cycle in progress, the
