UNITED KINGDON (13-Oct-00) -- The W78E516 microcontroller from Winbond is the manufacturer's first 8051 derivative device to offer In-System Programming (ISP). It is also the industry's first 8051based device to provide two separate on-board flash ROM's - 64k of application ROM (APROM), and a loader ROM (LDROM) of 4k. Either ROM can program the other without external programming voltages or hardware. And, because both ROMs are blank when the devices are manufactured, software developers are free to implement their own loader program rather than being tied to a specific serial type interface.
These devices are normally supplied either blank or pre-programmed with a boot loader that allows the APROM to be programmed by a serial connection to a PC. Because either ROM can program the other, developers can program the device with application code, then program the LDROM with a bespoke boot loader program. Source code for the LDROM is freely available from Flint, and may be modified and reprogrammed into the LDROM either via the APROM or a standard device programmer.
ISP functions available on the W78E516 are erase, read and write, and 'act on the alternative ROM to that currently selected'. Access is through four registers; address pointers SFRAH and SFRAL, SFRFD which contains data read from
or written to flash, and the control register SFRCN which selects the ISP mode. Erase is accomplished by a single command. All functions are carried out independently of the CPU, while the device is in "idle" mode.
Once the controlling registers are programmed, the device is put into an idle mode, where the CPU clock is disabled but peripherals and interrupt logic remain active. Usually a timer generates an interrupt after a predefined time, based on how long the ISP function takes to execute. This interrupt returns the CPU to active mode so that the device can continue ISP services or normal operation.
During normal operation, the W78E516 boots from APROM, jumping to the LDROM under software control when required. It is also possible to force the device to boot from the 4k LDROM via hardware - F04KBOOT mode. An F04KBOOT flag allows the system to distinguish between normal or forced execution of LDROM code, for example instigating a software reset if not set, or waiting for a hardware reset if set. The F04KBOOT flag can also be used to trigger a hardware test routine within an application.
Supporting this programmability on W78E516 (and other 8051 type devices), Flint's development platform is based on hardware that connects to the standard 40-pin DIL 8051 socket and allows code to be downloaded to the device and executed in-situ.
The heart of the system is a W78E516 programmed with a boot loader, running from an 11.0592MHz crystal and connected to the PC via a serial interface. A PC application allows users to select a .bin file and download it to the device while in F04KBOOT mode. The program first erases the APROM, and then programs and verifies the device with the selected file. In this way the APROM can be fully utilised by the programmer - there is no overhead of a monitor program or operating system. File size checking is also provided, to ensure that the file is no greater than 64k and data are verified during file transfer.
The system was designed for use with breadboard prototype systems. Because of this, a standard 80C5X 40-pin DIL pin-out is provided, compatible with standard devices and with third-party adapters for conversion to PLCC or QFP footprint.
A key factor in the hardware design is that as many I/O lines as possible are kept free for use. Because the PLCC version of the device has an extra four-bit port, this is used to drive an LED to indicate that the boot loader is running and therefore the device is waiting for code to be downloaded to the APROM. The port is also used to invoke F04KBOOT mode. The only other two I/O lines used for the ISP function are RXD and TXD. Connecting these ports to DIP switches allows users to choose between connection to the board's RS232 driver during program download; or to the pins of the 40-pin DIL header when programs are running and require serial communications. The system further allows control of the /EA input, used to switch between external and internal data access. All bus control signals are also available, giving maximum flexibility in expanded memory applications. The only pins unavailable to the developer are reset and the oscillator pins. Most of the device resources remain available to the user.
A number of new ISP devices are becoming available from Winbond, such as a low-voltage version of the W78E516 and the W78LE58, again a low voltage device which features a 32k APROM and 4k LDROM. Either of these devices can be
used with the ISP kit, and may be ordered separately.
When coupled with a public-domain 8051 assembler or C compiler, the result is an extremely low cost 8051 development system, where maximum MCU resources are accessible to the developer, and software overheads are kept to a minimum.
For more information on the ISP kit and to download the associated programs, please visit the Flint website, http://www.flint.co.uk.
About Flint Distribution
Flint is the UK's leading specialist distributor covering semiconductors, smart card technology, connectors, passives and discretes. Its silicon line-up now includes microcontrollers, telecommunications ICs and a full range of volatile and non-volatile memory amongst other LSI and VLSI devices. Flint's fine-pitch connector stock profile is the most comprehensive in the industry, and includes the SM ranges of AMP, Molex, Hirose JAE and JST as well as electromechanical devices from Omron and other manufacturers. Flint's extensive portfolio of chip passives and discretes is well known throughout the industry.
Flint Smart, a division of Flint Distribution, offers a complete portfolio of components and sub-systems required to implement Smart Card technology into security, retail, access control, healthcare IT applications. Flint provides cards, readers, acceptors, development kits and the associated devices from industry leaders such as Gemplus, Omron, NEC ACS, JAE, AMP and Molex.
Flint Distribution had an annual turnover of £15.3million in the 1999/2000 financial year. It publishes the Flint Navigator interactive SM component guide to over 15,000 lines kept in stock from over 40 franchises.