Auxiliary Port Arbitration - STMicroelectronics SPC572L series Reference Manual

e200z215An3 Nexus 3 Module
order bit so that it can end on a port boundary.
For example, if the nex_mdo[n:0] port is 2 bits wide, and the unique portion of an
indirect address TCODE is 5 bits, then the remaining 1 bit of nex_mdo[n:0] must be
packed with a 0.
66.20

Auxiliary port arbitration

In a multi-Nexus environment, the Nexus 3 module must arbitrate for the shared Nexus port
at the SoC level.The request scheme is implemented as a 2-bit request with various levels
of priority. The priority levels are defined in
receive a 1-bit grant signal (nar_aux_grant) from the SoC level arbiter. When a grant is
received, the Nexus 3 module will begin transmitting its message following the protocol
outlined in
port, by asserting the nex_aux_busy signal, until the MSEO state machine reaches the
"End Message" state.
Request level
No Request
Low Priority
High Priority
66.21 Examples
The following are examples of Program Trace and Data Trace Messages.
Table 1114
configuration.
configuration.
Note that T0 and S0 are the least significant bits where:
•
Tx = TCODE number (fixed)
• Sx = Source processor (fixed)
•
MAP = (always set to 0)
• Ix = Number of instructions (variable)
•
Ax = Unique portion of the address (variable)
Note that during clock 13, the nex_mdo[n:0] pins are ignored in the single MSEO case.
1978/2058
Section 66.18.2, Pin
Table 1113. MDO request encodings
MDO request encoding
(nex_aux_req[1:0])
—
illustrates an example Indirect Branch Message with 2 MDO / 1MSEO
Table 1115 illustrates the same example with an 8 MDO / 2 MSEO
DocID027809 Rev 4
Table 1113
protocol. The Nexus 3 module will maintain control of the
00 No message to send
01 Message queue less than 1/2 full
10 Reserved
11 Message queue 1/2 full or more
below. The Nexus 3 module will
Condition of queue
RM0400