Texas Instruments SM320C6455-EP manual CPU DSP Core Description

SM320C6455-EP

FIXED-POINT DIGITAL SIGNAL PROCESSOR

www.ti.com

SPRS462B – SEPTEMBER 2007 – REVISED JANUARY 2008

Table 2-1. Characteristics of the C6455 Processor (continued)

Process Technology

Product Status(2)

Device Part Numbers

HARDWARE FEATURES

μm

Product Preview (PP), Advance Information (AI), or Production Data (PD)

(For more details on the C64x+™ DSP part numbering, see Figure 2-13)

C6455

0.09μm

PD

TMS320C6455ZTZ7,

TMS320C6455ZTZ8,

TMS320C6455ZTZ

(2)PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

2.2CPU (DSP Core) Description

The C64x+ Central Processing Unit (CPU) consists of eight functional units, two register files, and two data paths as shown in Figure 2-1. The two general-purpose register files (A and B) each contain thirty-two 32 bit registers for a total of 64 registers. The general-purpose registers can be used for data or can be data address pointers. The data types supported include packed 8 bit data, packed 16 bit data, 32 bit data, 40 bit data, and 64 bit data. Values larger than 32 bits, such as 40 bit-long or 64 bit-long values are stored in register pairs, with the 32 LSBs of data placed in an even register and the remaining 8 or 32 MSBs in the next upper register (which is always an odd-numbered register).

The eight functional units (.M1, .L1, .D1, .S1, .M2, .L2, .D2, and .S2) are each capable of executing one instruction every clock cycle. The .M functional units perform all multiply operations. The .S and .L units perform a general set of arithmetic, logical, and branch functions. The .D units primarily load data from memory to the register file and store results from the register file into memory.

The C64x+ CPU extends the performance of the C64x core through enhancements and new features.

Each C64x+ .M unit can perform one of the following each clock cycle: one 32 x 32 bit multiply, two 16 x 16 bit multiplies, two 16 x 32 bit multiplies, four 8 x 8 bit multiplies, four 8 x 8 bit multiplies with add operations, and four 16 x 16 multiplies with add/subtract capabilities (including a complex multiply). There is also support for Galois field multiplication for 8 bit and 32 bit data. Many communications algorithms such as FFTs and modems require complex multiplication. The complex multiply (CMPY) instruction takes for 16 bit inputs and produces a 32 bit real and a 32 bit imaginary output. There are also complex multiplies with rounding capability that produces one 32 bit packed output that contain 16 bit real and 16 bit imaginary values. The 32 x 32 bit multiply instructions provide the extended precision necessary for audio and other high-precision algorithms on a variety of signed and unsigned 32 bit data types.

The .L or (Arithmetic Logic Unit) now incorporates the ability to do parallel add/subtract operations on a pair of common inputs. Versions of this instruction exist to work on 32 bit data or on pairs of 16 bit data performing dual 16 bit add and subtracts in parallel. There are also saturated forms of these instructions.

The C64x+ core enhances the .S unit in several ways. In the C64x core, dual 16 bit MIN2 and MAX2 comparisons were available only on the .L units. On the C64x+ core they also are available on the .S unit, which increases the performance of algorithms that do searching and sorting. Finally, to increase data packing and unpacking throughput, the .S unit allows sustained high performance for the quad 8 bit/16 bit and dual 16 bit instructions. Unpack instructions prepare 8 bit data for parallel 16 bit operations. Pack instructions return parallel results to output precision including saturation support.

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