28.5.3. Prefetcher Disabled Mode Interface
The following describes the interfaces that are applicable only when Prefetcher is disabled.
Descriptor Agent Interface (descriptor_slave)
| Signal Name | Direction | Type | Description |
|---|---|---|---|
| descriptor_slave_write | Input | Avalon® Memory-Mapped Agent | Write transfer into the descriptor FIFO. |
| descriptor_slave_byteenable [15:0] or [31:0] | Input | Enable the byte lanes during write transfer into the descriptor FIFO. | |
| descriptor_slave_writedata [127:0] or [255:0] | Input | Data of the descriptor write transfer into the descriptor FIFO. Refer to the Descriptor Format (without Prefetcher) section for data definition. Standard descriptor: 128-bit width Extended descriptor: 256-bit width |
|
| descriptor_slave_waitrequest | Output | mSGDMA IP asserts waitrequest when unable to respond to the descriptor write request. |
Response Port (response)
The response port provides response information from the dispatcher block upon completion of each descriptor execution to the host. The response port can be set to disabled, memory-mapped, or streaming, by configuring the parameter Response Port. The response port is not applicable if mSGDMA IP is configured as Memory-Mapped to Streaming transfer.
Avalon® -MM Response Agent Interface
| Signal Name | Direction | Type | Description |
|---|---|---|---|
| response_address | Input | Avalon® Memory-Mapped Agent | The read address to access the response CSR. |
| response_read | Input | Read access to the response CSR. | |
| response_byteenable [3:0] | Input | Enable the byte lanes during read access to the response CSR. | |
| response_readdata [31:0] | Output | Data in response to the read access of the response CSR. | |
| response_waitrequest | Output | mSGDMA IP asserts waitrequest when unable to respond to the read request. |
Avalon® -ST Response Source Interface
| Signal Name | Direction | Type | Description |
|---|---|---|---|
| response_ready | Input | Avalon® Streaming Source | Indicates that the sink can accept response data when ready is asserted high. |
| response_valid | Output | Indicates that the response data from the dispatcher is valid. | |
| response_data [255:0] | Output | Indicates the response data transfer from dispatcher to user’s Avalon® -ST sink interface. |
| Signal Name | Description |
|---|---|
| 31 - 0 | Actual bytes transferred [31:0] 47 |
| 39 - 32 | Error [7:0]47 |
| 40 | Early termination47 |
| 41 | Transfer complete IRQ mask 48 |
| 49 - 42 | Error IRQ mask47/48 |
| 50 | Early termination IRQ mask47/48 |
| 51 | Descriptor buffer full 49 |
| 255:52 | Reserved |
- Actual bytes transferred—determines how many bytes transferred when the mSGDMA is configured in Avalon® -ST to Avalon® -MM mode with packet support enabled. Since packet transfers are terminated by the IP providing the data, this field counts the number of bytes between the start-of-packet (SOP) and end-of-packet (EOP) received by the write host. If the early termination bit of the response is set, then the actual bytes transferred is an underestimate if the transfer is unaligned.
- Error—determines if any errors were issued when the mSGDMA is configured in Avalon® -ST to Avalon® -MM mode with error support enabled. Each error bit is persistent so that errors can accumulate throughout the transfer.
- Early Termination—determines if a transfer terminates because the transfer length is exceeded when the mSGDMA is configured in Avalon® -ST to Avalon® -MM mode with packet support enabled. This bit is set when the number of bytes transferred exceeds the transfer length set in the descriptor before the end-of-packet is received by the write host.
IRQ Interface (csr_irq)
This interface indicates to the host on the interrupt event occurrence happened with the mSGDMA IP.
- transfer completion
- early termination (applicable only for Streaming to Memory-Mapped configuration)
- error detection (applicable only for Streaming to Memory-Mapped configuration)
When the Prefetcher is disabled, the IRQ is generated from the dispatcher block.
Upon receiving the interrupt assertion from mSGDMA IP, the software should poll for the STATUS register. The IRQ status bit is set by hardware and cleared by software. To clear this bit, software needs to write a 1 to this bit. The IRQ status bit is set when a hardware event has a higher priority than a clear by a software event.
| Signal Name | Direction | Type | Description |
|---|---|---|---|
| csr_irq_irq | Output | Interrupt sender | Indicates the interrupt event occurrence. This signal remains asserted as long as the irq bit of the Status register is still asserted and not cleared by software. |