Visible to Intel only — GUID: iga1401397406406
Ixiasoft
Visible to Intel only — GUID: iga1401397406406
Ixiasoft
32.6.3. Register Maps
The control/status register has a 32-bit interface without byte-enable logic, and therefore cannot be properly accessed by a host with narrower data width than itself. To ensure correct operation of the core, always access the register with a host that is at least 32 bits wide.
32-bit Word Offset (Byte Offset) | Register Name | Reset Value | Description |
---|---|---|---|
base + 0 (0x0) | status | 0 | This register indicates the core’s current status such as what caused the last interrupt and if the core is still processing descriptors. See the status Register Map table for the status register map. |
base + 1 (0x4) | version | 1 | Indicate the hardware version number. Only being used by software driver for software backward compatibility purpose. |
base + 4 (0x10) | control | 0 | This register specifies the core’s behavior such as what triggers an interrupt and when the core is started and stopped. The host processor can configure the core by setting the register bits accordingly. See the Control Register Bit Map table for the control register map. |
base + 8 (0x20) | next_descriptor_pointer | 0 | This register contains the address of the next descriptor to process. Set this register to the address of the first descriptor as part of the system initialization sequence. Intel recommends that user applications clear the RUN bit in the control register and wait until the BUSY bit of the status register is set to 0 before reading this register. |
Bit | Bit Name | Access | Description |
---|---|---|---|
0 | IE_ERROR | R/W | When this bit is set to 1, the core generates an interrupt if an Avalon® -ST error occurs during descriptor processing. (1) |
1 | IE_EOP_ENCOUNTERED | R/W | When this bit is set to 1, the core generates an interrupt if an EOP is encountered during descriptor processing. (1) |
2 | IE_DESCRIPTOR_COMPLETED | R/W | When this bit is set to 1, the core generates an interrupt after each descriptor is processed. (1) |
3 | IE_CHAIN_COMPLETED | R/W | When this bit is set to 1, the core generates an interrupt after the last descriptor in the list is processed, that is when the core encounters a descriptor with a cleared OWNED_BY_HW bit. (1) |
4 | IE_GLOBAL | R/W | When this bit is set to 1, the core is enabled to generate interrupts. |
5 | RUN | R/W | Set this bit to 1 to start the descriptor processor block which subsequently initiates DMA transactions. Prior to setting this bit to 1, ensure that the register next_descriptor_pointer is updated with the address of the first descriptor to process. The core continues to process descriptors in its queue as long as this bit is 1. Clear this bit to stop the core from processing the next descriptor in its queue. If this bit is cleared in the middle of processing a descriptor, the core completes the processing before stopping. The host processor can then modify the remaining descriptors and restart the core. |
6 | STOP_DMA_ER | R/W | Set this bit to 1 to stop the core when an Avalon® -ST error is encountered during a DMA transaction. This bit applies only to stream-to-memory configurations. |
7 | IE_MAX_DESC_PROCESSED | R/W | Set this bit to 1 to generate an interrupt after the number of descriptors specified by MAX_DESC_PROCESSED are processed. |
8 .. 15 | MAX_DESC_PROCESSED | R/W | Specifies the number of descriptors to process before the core generates an interrupt. |
16 | SW_RESET | R/W | Software can reset the core by writing to this bit twice. Upon the second write, the core is reset. The logic which sequences the software reset process then resets itself automatically. Executing a software reset when a DMA transfer is active may result in permanent bus lockup until the next system reset. Hence, Intel recommends that you use the software reset as your last resort. |
17 | PARK | R/W | Setting this bit to 0 causes the SG-DMA controller core to clear the OWNED_BY_HW bit in the descriptor after each descriptor is processed. If the PARK bit is set to 1, the core does not clear the OWNED_BY_HW bit, thus allowing the same descriptor to be processed repeatedly without software intervention. You also need to set the last descriptor in the list to point to the first one. |
18 | DESC_POLL_EN | R/W | Set this bit to 1 to enable polling mode. When you set this bit to 1, the core continues to poll for the next descriptor until the OWNED_BY_HW bit is set. The core also updates the descriptor pointer to point to the current descriptor. |
19 | Reserved | ||
20..30 | TIMEOUT_COUNTER | RW | Specifies the number of clocks to wait before polling again. The valid range is 1 to 255. The core also updates the next_desc_ptr field so that it points to the next descriptor to read. |
31 | CLEAR_INTERRUPT | R/W | Set this bit to 1 to clear pending interrupts. |
Note :
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Intel recommends that you read the status register only after the RUN bit in the control register is cleared.
Bit | Bit Name | Access | Description |
---|---|---|---|
0 | ERROR | R/C (1) (2) | A value of 1 indicates that an Avalon® -ST error was encountered during a transfer. |
1 | EOP_ENCOUNTERED | R/C | A value of 1 indicates that the transfer was terminated by an end-of-packet (EOP) signal generated on the Avalon® -ST source interface. This condition is only possible in stream-to-memory configurations. |
2 | DESCRIPTOR_COMPLETED | R/C (1) (2) | A value of 1 indicates that a descriptor was processed to completion. |
3 | CHAIN_COMPLETED | R/C (1) (2) | A value of 1 indicates that the core has completed processing the descriptor chain. |
4 | BUSY | R (3) | A value of 1 indicates that descriptors are being processed.
This bit is set to 1 on the next clock cycle after the RUN bit is asserted and does not get cleared until one of the following event occurs:
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5 .. 31 | Reserved | ||
Note :
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