A high-reliability 32-bit Flash microcontroller for safety-critical applications.
Common to all safety critical applications is that the code and data in these applications have to be as safe as possible. The H8SX/1725F has been developed for high reliability industrial and medical applications. It also has the high reliability that Class III/IV (according to European MEDDEV association classification) medical applications demand. In the medical field, the device is qualified even for designs that include life-support applications. High reliability connectivity interfaces are often based on CAN interfaces, not only in automotive but also as standard in industrial areas. In many developments, logged data should be stored in an archive for tracking long term trends.
For these cases, the H8SX/1725F provides an integrated data Flash so that applications can effectively use 480Kcycles when using blocks consecutively. This function is useful in long-term medical data loggers that record vital signs over days, weeks or even months to track down medical conditions that are difficult to diagnose. Beyond medical applications, there are many industrial applications with similar requirements such as Automatic Teller Machines (ATM) or cash registers, which have to securely logg transaction data so that the reports generated form the data cannot be subject to repudiation.
MONOS - the leading edge embedded Flash technology
MONOS (Metal Oxide Nitride Oxide Silicon) Flash is world's fastest embedded Flash technology at 12.5ns read access time in the H8SX/1725F and 10ns in the H8SX/1725SF in 2009. So far this technology has focused on speed, now the H8SX/1725F has a split embedded MONOS Flash module, 256kByte high speed Flash for code and 16kByte high endurance Flash for data. The endurance is 30 000 e/w cycles for the Data Flash. By using blocks consecutively, applications can effectively use 480Kcycles. The non-conducting nitride floating gate helps make the MONOS Flash technology extremely reliable. With this technique it is impossible for a defect to have a negative effect on the charges trapped at the nitride layer. Only charges near the defect/disturbance are affected, thus effectively providing built-in redundancy.
The new Flash module is also very fast to program. Programming time has been reduced by approximately two thirds, from around 10 seconds for the entire 256KByte to only 3 seconds. Programming can take place across the entire temperature range of "40C to 85C. The benefit is reduced manufacturing cost, as flashing the MCU during production is faster.
Data retention is guaranteed as 15 years. Finally, the new module has a background operation mode (BGO) that enables executing code from Flash whilst programming other Flash areas.
MONOS Flash is the only process-scalable embedded Flash technology. Renesas uses 180/150/90nm now and will scale MONOS Flash to 65 and 45nm. MONOS Flash will be used by Renesas to integrate up to 8MB of monolithic embedded Flash into MCUs. The H8SX/1725 MCU eliminates the trade-off and gives engineers the best of both worlds: high speed & high endurance! Hence the module can be used to replace external EEPROM (electrically erasable and programmable read only memory) previously provided for data storage purposes, helping to achieve both parts count and cost reductions.
Numerous high reliability features
The H8SX/1725F has been designed to meet the high standards of reliability for safety critical applications. The specific reliability features are listed below.
• Design rules set for high reliability (Q1 grade in Renesas terminology).
• 10ppm maximum field failure rate target. Actual track record for products in this technology is below 1ppm field failure rate.
• MONOS Flash is inherently highly reliable due to non-conducting floating gate that prevents disturbances from affecting all charges. This is like built-in redundancy.
• Sophisticated mechanisms against accidental or malicious Flash read/write/erase. Separate product information Flash area for Device ID, Device Revision and Software revision.
• RAM with Error Correction Code or parity bit and other safety mechanisms.
• 2x RCAN (with all relevant certifications) as the best possible interface for high-reliability communication in industrial/medical systems.
• External oscillation stoppage detection circuit with built-in oscillation circuit for controlled emergency shutdown.
• Cyclic Redundancy Check (CRC) hardware to speed up error checking in data streams.
• 5V power supply and signals provide high Signal-to-Noise-Ratio (SNR). Positive for increased signal integrity.
• ADC has internal self diagnosis feature to detect malfunction.
• Highly reliable 100-pin QFP package with 0.5mm pin pitch and copper lead frame.
The modern CISC H8SX CPU core has 8 general purpose registers (picture 1 : H8SX CPU Core Diagram), each 32-bit wide and delivers 1 DMIPS/MHZ performance, which is fully supported by the zero-wait MONOS Flash as well as by the fast 24kByte RAM. The H8SX CPU also has a 16x16-bit multiplier/divider hardware that greatly benefits the execution speed of DSP-type maths algorithms.
Picture 1: H8SX CPU Core diagram
The device has 2 modules to support the CPU by taking care of data movements. These are: A 4-channel DMA module that supports many peripheral modules and all memory areas with normal, repeat and block transfer modes in cycle-steal or burst fashion. Address updates can be fixed-address, offset-addition, increment or decrement by 1, 2 or 4. A multi-channel Data-Transfer-Controller (DTC x 77 channels) which can serve all peripherals and memories and enables chain transfers (multiple transfers triggered by a single event). This module is very flexible and just a bit slower in its peak transfer rate, which of course does not matter if you use it to serve a slow peripheral such as a SCI. Neither the CPU nor the peripheral will notice any difference to a normal DMA.
The peripheral set also comprises a 2-channel CAN, 2-channel SCI, 4-channel High-speed serial interface, a watchdog timer and a 16-channel ADC. A specific self-diagnosis feature supports reliability and safety operating the CAN modules. There are two SAR-type 10-bit ADC units with 8 channels and a 1.25 s conversion time per A/D converter. Each ADC module has single- and scan-mode and one 16-bit wide result registers per channel. Each unit has a sample & hold circuit and can be triggered by software (single and scan mode), by timer or a trigger pin. Two independent units each with 8 data registers are implemented to reduce interrupt load. This A/D unit has an internal self-diagnosis feature to detect malfunction.
The H8SX/1725F has a vast array of timers, a total of 22 channels. The two most powerful modules are the two Timer Pulse Units (TPU), which each comprise six channels of 16-bit wide timers. Each channel has up to 16 input capture/output compare associated with the six channels. The resolution is at full clock speed, i.e. 15.6ns at 64MHz and will scale as we introduce faster derivatives to 12.5ns. The TPUs have many modes, can be cascaded, buffered, can trigger the ADC and have 26 interrupt vectors linked to each unit. It also features a Programmable Pulse Generator (PPG) that has real-time outputs to drive stepper motors.
Picture 2: H8SX/1725 Block diagram
The TPU can trigger the Programmable Pulse Generators (PPG) which provide 16 real-time outputs in 4 groups. The PPGs are designed to drive stepper motors but can be used for anything that requires jitter-free streams of data patterns. There are two PPG units so the device can control up to 8 stepper motors. Two channels each can be cascaded to add yet more 16-bit timers to the 12 channels in the TPUs. Then there are two special-function timers. The Watchdog Timer (WDT) is an 8-bit timer with an 8-way-prescaler that benefits system safety by generating a reset to the device when runaway code has stopped normal system operation. Outlook
The H8SX/1725F is now available in a RoHS-compliant 100-pin copper lead-frame LQFP. An evaluation kit SDK1725, supported by the E10A-debugger, is available. C-Compiler options are the Renesas C++ Compiler as well as the free-of-charge GNU C Compiler from KPIT Cummins Infosystems Limited (www.gnuh8.com). CAN drivers and a CANopen middleware package is under development and planned for Feb 2009. Further line up derivates to the H8SX/1725 are planned for 2009, with increased speed up to 80MHz and double the integrated memory.
 H8SX/1725: Technical details available online: www.renesas.eu
Guenter Plechinger is Product Marketing Engineer for Renesas Technology Europe
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