Hitachi Ltd is the arch-rival to NEC Corp in Japan’s silicon-based invasion of the US. While NEC readies the V800 range of chips to try and net 20% of the 32-bit Personal Digital Assistant market, Hitachi is preparing its own series, the SH703x family, aimed at the same sector. The kickback from the US and the UK comes in the form of the ARM and Hobbit chips from Advanced RISC Machines Ltd and AT&T Co respectively, both of which are already in production. Motorola Inc has also waded in, announcing its 68349 chip. This is a data-shifting processor designed to be used in hand-held communications devices with sister chips which handle communications and other functions. Hitachi could well lock antlers with both the Japanese and US-bred chips in the Personal Digital Assistant market. The general definition of a Personal Digital Assistant seems to be a handheld device with communications functionality, although Hitachi says that its chip will spill over into all handheld computing products. Kevin Hayward, microprocessor product manager for Hitachi UK, predicts that the Personal Digital Assistant market will develop in the US first, subsequently blossoming in Northern Europe. Interestingly, Hitachi management in the US privately believes that the Personal Digital Assistant market is ‘a tough row to hoe’, because most of the products are presently vapourware. One source held the opinion that the chips would initially be used as embedded controllers in other devices, with Personal Digital Assistant implementations arriving later. The SH703x series is being touted as an embedded controller and central processing unit by Hitachi – effectively a Personal Digital Assistant on a chip. The family will initially incorporate two chips, SH7032 and the SH7034.

Labouring

The difference between the two lies in the memory: the 7032 has 8Kb of on-chip RAM, whereas the 7034 has only half this amount but more than makes up for it with 64Kb of ROM, which can be used by designers to hold embedded software programs for a complete single chip solution. Both chips include a 32-bit RISC-based CPU and a 32-bit address bus. Although they hobble along on a 16-bit external bus, there is a 22-bit unmultiplexed data bus for designers that want to address up to 4Gb of RAM. The chips run at either 5V or 3.3V in power-saving mode. Clock speed reaches 20MHz at the top end and drops to 12.5MHz at the lower Voltage, with a MIPS rating of 16 at the higher power level. NEC pips the Hitachi chips at the post here, with an 18 MIPS performance rating. Unlike NEC’s family, though, the Hitachi range’s embedded functionality makes it more or less self-sufficient. Hitachi is labouring this point, because it knows that the NEC range does not have any internal peripherals or indeed the glue logic needed to connect to external ones, let alone external memory (CI No 2,210). The designers have to tack on the logic to implement that functionality themselves. The Hitachi chips include an Analogue to Digital Converter using eight channels, which could theoretically take a variety of different inputs including speech and pen input for handwriting recognition. In addition, the system has a four-channel Direct Memory Access engine for reaching memory more quickly. Because it has four channels, up to four concurrent memory locations can be accessed at once, without disturbing the processor – two of them externally. Also included are two serial ports which can be programmed synchronously or asynchronously at baud rates decided by the chip’s internal clock – up to 5M-bits per second can be obtained. There is a pattern generator for general purpose functions including motor control, and there is a central timing controller containing five timers with their own registers for capture and output purposes.

By Danny Bradbury

The SH703x chips both have 32-bit central processing units, and 32-bit registers. There are more of them on the NEC, though the V810 has 32, whereas both the Hitachi chips make do with 16. The Hitachi chips include some 16 and some 32-bit instructions, and use a s

horter integer multiplication process. The multiplier on this chip takes three cycles to produce a 32-bit result from two 16-bit operands, whereas the V810 takes 13 cyles. The SH703x chips use latencies to accumulate the result in another register during the three-cycle operation, whittling the multiply operation down to 150nS. This makes it possible to use the chip for low-end signal processing functions, according to Hitachi. Unlike the NEC range, all chips in the Hitachi SH703x series have power-down modes – not one, but two. There is a sleep mode in which the CPU freezes but peripherals are still acknowledged, and a standby mode which keeps the CPU running but stops all the peripherals. Whether this makes up for the NEC range’s ability to run at 2.2V is another matter. Like the NEC chips, the SH chips are to be fabricated in 0.8 microns, the same as the ARM chip and the V800. The Hobbit is in a more conservative 0.9 process. The 7032 uses 532,000 transistors whereas the 7034 has 900,000 of them, because of the 64Kb of ROM that it includes. The V810 uses only 240,000 transistors due to its lack of memory. This makes it smaller than the Hitachi chips, measuring in at 7.7mm square, compared with the SH7032’s 9.5mm by 9.7mm. The SH chips score over their opponents with their rich feature-set. They are evidently designed as easy, pre-defined parts for designers, which is no bad thing except that this could be seen as inflexible by some OEM csutomers that don’t need all the functionality or that want to implement alternative peripheral options. Hitachi has partially catered for these people by making all of the peripheral input-output pins reassignable for general input-output, so that the chip can be used to control other subsystems. It has not ruled out work on a core product for custom ASIC development, but will not comment on how much functionality will be stripped out, if any. The ARM chip has a number of basic similarities to the SH 7034, notably the RISC CPU, the 32-bit register size and the 4Kb RAM. The Direct Memory Access function is available in a separate chip. For those wanting embedded functionality the ARM250 includes DMA functionality, input-output and Interrupt controllers, serial communications functionality and – something the Hitachi lacks a video controller. Basic ARM technology is already available in a macrocell, the ARM6, which can be used as the core technology for custom ASICs by ARM’s partners, including VLSI Technology Inc and GEC Plessey Semiconductors Ltd.

Criticised

The use of partners to fabricate chips in response to customer demand makes the ARM chip more flexible than the Hitachi or the NEC chip could ever be on their own.Advanced RISC Machines Ltd criticised Hitachi America for its lack of software development for the SH7000 range. Mike Muller, marketing director for the Camnbridge company, says that the chip needs a decent software tool set to bring it into the market. ARM’s tool set seems to be watertight, or so Apple Computer Inc and 3DO Co Inc would believe. Both companies have included the chip in their own product specifications, 3DO opting for the basic ARM60 processor and Apple slotting the ARM610 into the Newton. Hayward says that Hitachi’s Eurodesk division is developing tools for the system which must be in place before the silicon starts shipping. This was reinforced by US staff who said that other toolsets for the chip would appear in the public domain, to increase access for developers and fuel third party software products for the SH family. With Hitachi promising that the in-house software will be ready in the second half of the year, and with sample quantities of the chip already available, the Japanese company should be ready to run up the glowing red sun standard by Christmas.