Send command and parameters from stack to firmware to perform some action based on stack state or in response to AL event interrupt or SYNC interrupt from ESC.
| Command | Id | Param1 | Param 2 | Return Val | Remarks |
| CMD_DL_USER_ACK_MBX_READ | 4 | address | length | NA | Indicate PDI side mailbox read completion to firmware |
| CMD_DL_USER_ACK_MBX_WRITE | 5 | address | length | NA | Indicate PDI side mailbox write to firmware |
| CMD_DL_USER_EEPROM_CMD_ACK | 6 | NA | NA | NA | Acknowledge EEEPROM emulation command execution by ARM host stack |
| CMD_DL_USER_READ_SYNC_STATUS | 7 | sync_sel | NA | NA | Indicate SYNC0/1 status register read by PDI to firmware |
| CMD_DL_USER_READ_AL_CONTROL | 8 | NA | NA | NA | Indicate AL control register read by PDI to firmware |
| CMD_DL_USER_WRITE_AL_STATUS | 9 | NA | NA | NA | Indicate AL status register write by PDI to firmware |
| CMD_DL_USER_READ_PD_WD_STATUS | 10 | NA | NA | NA | Indicate PD watchdog status register read by PDI to firmware updating register status |
| CMD_DL_USER_READ_SM_ACTIVATE | 11 | sm_index | NA | NA | Indicate SM activate register read by PDI to firmware |
| CMD_DL_USER_WRITE_SM_PDI_CTRL | 12 | (sm_index<<8) OR pdi control reg value | NA | NA | Indicate SM PDI control write to control SM from PDI to firmware |
| CMD_DL_USER_READ_LATCH_TIME | 13 | latch_sel | NA | NA | Indicate Latch0/1 time registest read by PDI to firmware |
| CMD_DL_USER_READ_SYS_TIME | 14 | NA | NA | NA | Indicate System Time register read by PDI to firmware |
| CMD_DL_USER_CLEAR_AL_EVENT_LOW | 15 | event_mask | NA | NA | Clear events not set in event_mask in AL event request register |
| CMD_DL_USER_SYSTIME_PDI_CONTROL | 16 | reg_sel | NA | NA | Indicate to the firmware DC register update from PDI side |
IMPORTANT NOTE on SUPPORT_CMDACK_POLL_MODE: EtherCAT firmware supports both poll mode and interrupt mode for command acknowledge. It is found that poll mode offers better latency in given scenarios but will waste CPU cycles busy waiting for command response from PRU. If you need to switch to command ack interrupt mode comment the define for SUPPORT_CMDACK_POLL_MODE in tiescbsp.h
1.8.20