SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The following applies when ISP5_CTRL[21] MFLAG = 1. The MFlag value is static.
The BL outputs cpriority[2:0] and cepriority[2:0] signals on its VBUS master port interface. On the VBUSM side, these signals are aligned with the request (creq). Both values actually repeat register input signals. The lower value (0) corresponds to the higher priority.
The MFlag signal does not need to be aligned with the request. The signal can change value anytime.
In the ISP VBUSM2 interface bridge, the cepriority signal is ignored and only the cpriority signal is used. Because the priority value is set up by a register setting, the value is not dynamically modified. Table 9-219 shows how the cpriority values are mapped to the interface MFlag signal, which is present on the ISP master interface and set in the ISP5_CTRL[3:1] VBUSM_CPRIORITY bit field.
MFlag[1:0] | Description |
---|---|
00 | Normal priority cpriority[2:0] = 4, 5, 6, 7 |
01 | Medium priority cpriority[2:0] = 2, 3 |
10 | Reserved |
11 | High priority cpriority[2:0] = 0, 1 |
The following applies when the ISP5_CTRL[21] MFLAG = 0. The MFlag value is dynamic.
This feature is enabled at reset. The purpose for dynamic MFlag generation is to monitor the FIFO levels. Thresholds are used to increase or decrease the MFlag values. There are different implementations for read and write requestors.
An individual MFlag value is generated for each FIFO and then ORed altogether and exported at the BL boundary. The MFlag signal generation does not affect the BL arbitration scheme.
Table 9-220 gives the low- and high-level priority thresholds for write initiators.
ISIF | H3A | IPIPE | RSZ | |
---|---|---|---|---|
Access type | Write | Write | Write | Write |
Buffer size | 64 × 128 | 64 × 128 | 48 × 128 | 64 × 136 |
50% low level | 32 × 128 | 32 × 128 | 24 × 128 | 32 × 136 |
75% high level | 48 × 128 | 48 × 128 | 36 × 128 | 48 × 128 |
Table 9-221 gives the low- and high-level priority thresholds for read initiators
IPIPEIF | ISIF-LSC | |
---|---|---|
Access type | Read | Read |
Buffer size | 64 × 128 | 32 × 128 |
25% buffer size | 16 × 128 | 8 × 128 |
50% buffer size | 32 × 128 | 16 × 128 |