UM0434 datasheet(372/390 Pages) STMICROELECTRONICS

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UM0434

Nexus3 module

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The Nexus auxiliary port arbitration pins are used when the Nexus3 module is implemented

in a multiple Nexus SoC that shares a single auxiliary output port. The arbitration is

controlled by an SoC-level Nexus port control module (NPC). Refer to

Chapter 12.13:

Auxiliary port arbitration on page 376,” for details on Nexus port arbitration.

12.11.2

Pin protocol

The protocol for the e200z3 processor transmitting messages through the auxiliary pins is

accomplished with the MSEO pin function outlined in

Table 273. Both single- and dual-pin

cases are shown.

nex_mseo_b[1:0] is used to signal the end of variable-length packets, and not fixed length

packets.

nex_mseo_b[1:0] is sampled on the rising edge of the Nexus3 clock, nex_mcko.

nex_evto_b

Event out. An output whose assertion indicates that one of two events

has occurred based on the bits in DC1[EOC].

nex_evto_b is held

asserted for 1 cycle of

nex_mcko:

– One (or more) watchpoints has occurred (from Nexus1) and

EOC = 00

– Debug mode was entered (

jd_debug_b asserted from Nexus1) and

EOC = 01

nex_evti_b

Event in. An input whose assertion initiates one of two events based

on DC1[EIC] (if the Nexus module is enabled at reset):

– Program trace and data trace synchronization messages (provided

program trace and data trace are enabled and EIC = 00).

– Debug request to e200z3 Nexus1 module (provided EIC = 01 and

this feature is implemented).

Table 272.

Nexus port arbitration signals

Nexus Port

Arbitration pins

Input/

Output

Description of arbitration pins

nex_aux_req[1:0]

Nexus auxiliary request. Output signals indicating to an SoC level

Nexus arbiter a request for access to the shared Nexus auxiliary port in

a multiple Nexus implementation. The priority encodings are

determined by how many messages are currently in the message

queues, see

Table 274).

nex_aux_busy

Nexus auxiliary busy. An output signal to an SoC level Nexus arbiter

indicating that the Nexus3 module is currently transmitting its message

after being granted the Nexus auxiliary port.

npc_aux_grant

Nexus auxiliary grant. An input from the SoC level Nexus port

controller (NPC) indicating that the auxiliary port has been granted to

the Nexus3 module to transmit its message.

ext_multi_nex_sel

Multiple Nexus select. A static signal indicating that the Nexus3

module is implemented within a multiple Nexus environment. If set,

port control and arbitration is controlled by the SoC-level arbitration

module (NPC).

Table 271.

Nexus3 auxiliary pins (continued)

Auxiliary pin

I/O

Description of auxiliary pins

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