Integrate Serial EEPROM & Flash Devices to Reduce Costs

In many applications, non-volatile memory needs are addressed by general-purpose serial-interface electrically erasable programmable read-only memories (EEPROM) or flash memory devices. These devices are used because they offer low pin counts, small packages, low-voltage operation, and low power consumption. Despite these advantages, designers still face the challenge of reducing board space and total system cost.

Common uses for these memory devices relate to system configuration, manufacturing, and security. Designers can obtain board space and cost reductions in these applications by instead using MAX^® II CPLDs, which offer an 8-Kbit flash storage block called user flash memory.

Table 1 shows a comparison of the costs and features of some solutions offering non-volatile memory and programmable logic. MAX II CPLDs deliver the lowest cost, provide a more flexible user interface to the memory, and are not prone to obsolescence.

Notes:

1. Pricing based on 100-unit list price
2. An example non-Altera CPLD is the Lattice Semiconductor LC4256V-75TN100C (priced at $17.60 for 100 units).

Applications for PLD-Based Non-Volatile Memory

Microprocessors, ASSPs, ASICs, and microcontrollers often require configuration data at power-up to boot up. Microprocessors and ASSPs use boot configuration data to define initial states and basic system information, such as bus widths. Typically, processors require between 256 and 1,000 bits of configuration data. ASSPs and ASICs require between 1,000 and 4,000 bits of configuration data. Many system boards use serial EEPROM or flash devices to store this configuration data.

The user flash memory in MAX II CPLDs also can be used in board design, where system designers are increasingly using serial EEPROMs instead of DIP switches and jumpers to configure their boards. This configuration data can control system parameters such as:

• Memory configuration
• IP or port address
• Peripheral address specification (e.g., USB)

Another user flash memory application can be found in the board manufacturing process, where an electronic identification code is often used to identify boards. These electronic IDs hold generic information and board-specific information such as:

• Date of manufacture
• Board serial number and product identification
• PC board and test program revision
• Software security code
• Power requirements

Using the user flash memory to store the electronic ID instead of serial EEPROM devices enables board manufacturers to use the Joint Test Action Group (JTAG) port to write and read it, potentially saving cost in those cases where edge connector pins or an additional header had previously been used.

Additional User Flash Memory Benefits

In addition to reducing the cost of non-volatile storage, user flash memory in MAX II CPLDs can:

• Reduce board space by eliminating serial EEPROMs, flash devices, and additional support circuitry such as external edge connector pins
• Simplify manufacturing flows by eliminating additional support circuitry and lowering costs associated with board mounting and programming serial EEPROMs and flash memory devices
• Obsolescence-proof designs since user flash memory is integrated in all MAX II devices
• Deliver a flexible user interface to memory, as the user flash memory can be interfaced via the MAX II device logic, giving users the flexibility to write to and read from the device in a variety of ways

For more information, read the Low-Cost Integration of Serial EEPROMs & Flash Memory Devices (PDF) white paper.

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