Specifications

Chapter 2 – Hardware Resources

34 PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Boo

Integrity Mechanisms

Memory Integrity Using Checksums

To ensure the integrity of the memory of the PL Smart Transceiver, the Neuron firmware maintains a number of

checksums. Each checksum is a single byte and is the two’s complement of the sum of all bytes it covers. These

checksums are verified during reset processing and also on a continual basis via a background diagnostic process. There

are three main checksums used to verify the integrity of the PL Smart Transceiver’s memory:

• Configuration image checksum

• Application image checksum

• System image checksum (off-chip system image only)

The configuration image checksum covers the network configuration information and communication parameters

residing in the on-chip EEPROM. The default behavior is that a configuration checksum error causes the device to go to

the unconfigured state. Refer to Table 2.12 for other options.

The application image checksum covers the application code in both on-chip EEPROM and any application code in off-

chip EEPROM, NVRAM, or flash memory. This checksum can optionally be extended to cover any application code in

off-chip ROM as well. The default behavior is that an application checksum error causes the device to go to the

applicationless state. Application read/write data residing in EEPROM, NVRAM, or flash is not checksummed. Refer to

Table 2.12 for other options.

Table 2.11 Checksum Coverage of PL Smart Transceiver Memory Areas

Memory Area Checksum

System image (optionally covered by application

checksum on the PL 3150)

System

Any off-chip ROM code (optionally covered by

Application checksum on the PL 3150)

Application

Any off-chip flash, EEPROM, or NVRAM code

Application

Any off-chip RAM code

Application

Configuration image

Configuration

All on-chip EEPROM code

Application

In the PL 3150 Smart Transceiver, all memory areas listed in Table 2.11 except for on-chip EEPROM code have their

own checksum so that checksum errors can be further isolated. An unconfigured or configured device continually

checks its application checksum in the background at the rate of 1 byte per iteration through the network processor’s

main loop (3 bytes per millisecond when running at 10MHz with no network activity).

The system image checksum covers the system image. It is only available when the system image resides in off-chip

memory and its use is optional. A system image checksum error always forces the device to the applicationless state.

No checksum is computed if the device is in the applicationless state.

The checksums are all verified during reset processing by the network processor and as part of the background

diagnostic process. The background diagnostic process causes the device to reset when an error is detected; no state

change occurs. It is assumed that any persistent error will be found by the reset processing.