STM's SoC for Set-Top Boxes

As set top boxes move close to invading our households, it's interesting to see that they are taking on so many of the attributes of computers. Unless they're substantially cheaper than a low-end PC that's kitted out for video, it's a wonder that some mom and pop computer shops aren't stitching together cheap computers with the idea that they'll be used in place of the new next big thing. STMicroelectronics' new ST40GX1 System-on-Chip (SoC) device combines a ST40 32-bit RISC microprocessor, a Gamma 2D graphics engine and compositor supporting six display planes, and a digital video encoder. The widget can be used stand-alone in web-enabled analog TV applications or with the STi5514 set-top box decoder for interactive digital TV apps. The ST40 processor is a member of the SuperH family of RISC engines that ST co-developed with Hitachi. The core provides a 166MHz, 300MIPS 32-bit CPU based on a two-way superscalar architecture, a 64-bit floating-point co-processor and on-chip instruction and data caches. STM says the CPU features an efficient load-store architecture, delayed branch instruction capability, and an on-chip multiplier, to allow high code density and fast program execution. The floating-point co-processor executes single (32-bit) and double (64-bit) precision operations and supports IEEE754-compliant data types and exceptions. Along with the floating-point multiply-and-accumulate, divide, and square root, the FPU performs 3D graphics and four-dimensional vector operations. The integrated graphics and video subsystem contains the Gamma 2D graphics accelerator, the Gamma compositor - which performs digital mixing of six display planes - and the video encoders. The architecture supports two digital video input streams and the six display planes allow for features like mixing two video sources, picture-in-picture, and hardware cursors to be implemented. The graphics subsystem supports SDRAM and DDR SDRAM.

The audio block gives you two PCM digital audio inputs and a PCM digital audio output, with internal sample rate conversion and digital mixing. In addition to its on-chip peripherals, including two serial ports, a general-purpose I/O port, timers, and real-time clock, the ST40GX1 has a set of interfaces to optional external peripherals. These include interfaces for a smart card, teletext insertion, infra-red control, a modem codec for software modem, and PCI and USB peripherals like DOCSIS and ADSL modems. An external memory interface supports burst-mode Flash memory and an optimized connection to the STi5514. The ST40GX1 is built using 0.18-micron CMOS technology and housed in a 35 x 35mm 456-pin BGA package. Samples are available now, with volume production scheduled for Q4, 2001.