FRAM-based MCU MSP430FR57xx design

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FRAM-based MCU MSP430FR57xx design [Copy link]

Mobile credit card reader application, where the unique differentiation value of the MSP430FR5739 can help solve multiple challenges. The MSP430FR5739 device features 16K embedded FRAM, 5 independent timers, hardware multiplier, DMA, ADC, and serial communication ports. When it comes to mobile credit card readers, not all readers are equal, and they all have a few different flavors:

(1) Simple magnetic stripe reader: This reader only supports an analog front end. The card data is read from the magnetic stripe and then transmitted to the phone.

(2) Magnetic Stripe Reader + Encryption: This reader supports an analog front end through an MCU that encrypts the data read from the card before transmitting it to the phone. This implementation is shown in the block diagram.

(3) Magnetic stripe reader + encryption + dynamic authentication: This adds an extra layer of protection by reading the composition of the magnetic stripe, which is said to be as unique as a fingerprint. The magnetic stripe information can then be paired with the card information to create unique read data that cannot be replicated. However, this method is very complex to implement and requires extensive modifications to existing readers, so it has not yet gained widespread popularity.

The figure shows a card reader that supports encryption. The MSP430FR5739 not only performs all the processing work after the card is swiped, but also transmits only the encrypted information to the phone. The ultra-low power MSP430 is ideal for this type of application because the card reader is generally powered by a battery-powered host device with very high energy constraints. Implementing encryption algorithms in software such as the one described in this application report consumes a lot of CPU cycles. The FR5739 device consumes less than 100uA/MHz and can enter standby mode when the reader is not in use, helping the card reader meet the most stringent power requirements. The 3-channel DMA and 32-bit hardware multiplier can effectively reduce the CPU load, further reducing the overall power consumption.

If writes are fast (8MBps), power is low, no pre-erase is required, and can be performed in byte blocks, then FRAM is used exactly like RAM. In applications where timing is critical, writing to non-volatile memory can sometimes put the application in a blocked state where interrupt processing is suspended until the memory write or erase is complete. This is not the case with FRAM, as writes can be completed in nanoseconds and no pre-erase is required.

In addition, many card readers also perform some form of tamper detection, which can check whether the device housing has been opened or tampered with in some way. On the MSP430FR5739 device, this can be done using any of the 26 interruptible general-purpose I/O pins.