3.3.14 Maximum Outstanding Transactions Registers

These registers determine how many Outstanding Transactions (OTs) are permitted when the OT regulator is enabled for the relevant slave interface.

Usage constraints
If you set the maximum OT size greater than that configured in the RTL, then the value of SIx_RW_MAX is written into the register. The minimum value of SIx_RW_MAX is 4. Writing values lower than 4 writes a value of 4 into the register.
Accessible using only Secure accesses, unless you set the Secure Access Register to permit Non-secure accesses.
Configurations
Available in all CCI-550 configurations.
An instance of this register exists for each slave interface.
Attributes
See 3.2 Register summary for more information.
The following figure shows the bit assignments.
Figure 3-12 qos_max_ot register bit assignments
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The following table shows the bit assignments.

Table 3-15 qos_max_ot register bit assignments

Bits
Name
Reset
Function
[31:8]
Reserved
-
-
[7:0]
max_ot
SIx_RW_MAX
The maximum number of OTs for the interface. This value is a combined issuing limit. It represents the maximum number of transactions that the upstream master can issue when the AR and AW channels are considered as one issuing source.

Note

Additional transactions can be issued into the CCI-550 at the boundary of the device. This is because of the presence of configurable registering between the boundary and the main trackers.
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