UM0434 datasheet(370/390 Pages) STMICROELECTRONICS

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UM0434

Nexus3 module

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12.10.7

Error handling

The Nexus3 module handles various error conditions as described in the following sections.

AHB Read/Write error

All address and data errors that occur on read/write accesses to the e200z3 AHB system

bus return a transfer error encoding on the

p_hresp[1:0] signals. If this occurs, the following

steps are taken:

The access is terminated without retrying, and RWCS[AC] is cleared.

RWCS[ERR] is set.

The error message is sent, TCODE = 8, indicating read/write error.

Access termination

The following cases are defined for sequences of the read/write protocol that differ from

those described in the above sections.

If RWCS[AC] is set to start read/write accesses and invalid values are loaded into RWD

or RWA, an AHB access error may occur. This is handled as described above.

If a block access is in progress, all cycles are not completed, and the RWCS register is

written. The original block access is terminated at the boundary of the nearest

completed access.

If RWCS[AC] is set, the next read/write access begins and the RWD can be

writtento/read from.

If RWCS[AC] is cleared, the read/write access is terminated at the nearest

completed access. This method can be used to break block accesses or terminate

them early.

Read/Write access error message

The read/write access error message is sent out when an AHB system bus access error,

read or write, has occurred.

Error information is messaged out in the format shown in

Table 269:

12.11

Nexus3 pin interface

This section details the Nexus3 pins and pin protocol.

The Nexus3 pin interface provides the function of transmitting messages from the message

queue to the external tools. It is also responsible for handshaking with the message queue.

12.11.1

Pins implemented

The Nexus3 module implements one

nex_evti_b and either one nex_mseo_b or two

nex_mseo_b[1:0]. It also implements a configurable number of nex_mdo[n:0] pins,

Table 269.

Error message format

(5 bits)

(4 bits)

(6 bits)

Error Code (00011)

Source Process

TCODE (001000)

Fixed length = 15 bits

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