ES_LPC435X_3X_2X_1X

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Errata sheet

Rev. 2 — 20 October 2012

4 of 11

NXP Semiconductors

ES_LPC435x/3x/2x/1x

Errata sheet LPC435x/3x/2x/1x

3.

Functional problems detail

3.1 C_CAN.1: Writes to CAN registers write through to other peripherals

Introduction:

Controller Area Network (CAN) is the definition of a high performance communication

protocol for serial data communication. The C_CAN controller is designed to provide a full

implementation of the CAN protocol according to the CAN Specification Version 2.0B. The

C_CAN controller allows to build powerful local networks with low-cost multiplex wiring by

supporting distributed real-time control with a very high level of security.

Problem:

On the LPC43xx, there is an issue with the C_CAN controller AHB bus address decoding

that applies to both C_CAN controllers. It affects the C_CAN controllers when peripherals

on the same bus are used. Writes to the ADC, DAC, I2C, and I2S peripherals can update

registers in the C_CAN controller. Specifically, writes to I2C0, MCPWM, and I2S can affect

C_CAN1. Writes to I2C1, DAC, ADC0, and ADC1 can affect C_CAN0. The spurious

C_CAN controller writes will occur at the address offset written to the other peripherals on

the same bus. For example, a write to ADC0 CR register which is at offset 0 in the ADC,

will result in the same value being written to the C_CAN0 CNTL register which is at offset

0 in the C_CAN controller. Writes to the C_CAN controller will not affect other peripherals.

Work-around:

Workarounds include: Using a different C_CAN peripheral. Peripherals I2C1, DAC, ADC0,

and ADC1 can be used at the same time as C_CAN1 is active without any interference.

The I2C0, MCPWM, and I2S peripherals can be used at the same time as C_CAN0 is

active without any interference. Another workaround is to gate the register clock to the

CAN peripheral in the CCU. This will prevent any writes to other peripherals from taking

effect in the CAN peripheral. However, gating the CAN clock will prevent the CAN

peripheral from operating and transmitting or receiving messages. This workaround is

most useful if your application is modal and can switch between different modes such as

an I2S mode and a CAN mode. Another workaround is to avoid writes to the peripherals

while CAN is active. For example, the ADC could be configured to sample continuously or

when triggered by a timer, before the CAN is configured. Afterwards, C_CAN0 can be

used since the ADC will operate without requiring additional writes.