Pin Protocol - STMicroelectronics SPC572L series Reference Manual

RM0400
The Nexus auxiliary port arbitration pins are used when the Nexus 3 module is implemented
in a multi-Nexus SoC that shares a single auxiliary output port. The arbitration is controlled
by an SoC level Nexus Aurora Router (NAR). Refer to
arbitration, for detail on Nexus port arbitration.
Nexus port Input/
arbitration pins Output
nex_aux_req[1:0]
nex_aux_busy
nar_aux_grant
ext_multi_nex_sel
66.18.2

Pin protocol

The protocol for the processor transmitting messages via the auxiliary pins is accomplished
with the MSEO pin function outlined in
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 Nexus 3 clock
(nex_mcko).
Single pin MSEO is not supported on the SPC572Lx.
nex_mseo_b function
Start of message
End of message
End of variable length packet
Message transmission
Idle (no message)
Figure 1184
Table 1111. Nexus port arbitration signals
Nexus Auxiliary Request (nex_aux_req[1:0]) output signals indicate to an SoC level
Nexus arbiter a request for access to the shared Nexus auxiliary port in a multi-Nexus
O
implementation. The priority encodings are determined by how many messages are
currently in the message queues (See
Nexus Auxiliary Busy (nex_aux_busy) is an output signal to an SoC level Nexus
O arbiter indicating that the Nexus 3 module is currently transmitting its message after
being granted the Nexus auxiliary port.
Nexus Auxiliary Grant (nar_aux_grant) is an input from the SoC level NAR that the
I
auxiliary port has been granted to the Nexus 3 module to transmit its message.
Multi-Nexus Select (ext_multi_nex_sel) is a static signal indicating that the Nexus 3
I module is implemented within a multi-Nexus environment. If set, port control and
arbitration is controlled by the SoC level arbitration module (NAR).
Table 1112. MSEO pin(s) protocol
illustrates the state diagram for single pin MSEO transfers.
DocID027809 Rev 4
Description of arbitration pins
Table
Table 1112. Both single and dual pin cases are
Single nex_mseo_b data
(serial)
1-1-0
0-1-1-(more 1's)
0-1-0
0's
1's
e200z215An3 Nexus 3 Module
Section 66.20, Auxiliary port
1113.)
Dual nex_mseo_b[1:0] data
11-00
00 (or 01)-11-(more 1's)
00-01
00's
11's
1975/2058
1982