Visible to Intel only — GUID: iga1401396006724
Ixiasoft
Visible to Intel only — GUID: iga1401396006724
Ixiasoft
24.2.3. Avalon® -MM Write Agent to Avalon® -ST Source
In this configuration, the input is an Avalon® -MM write agent with a width of 32 bits as shown in the FIFO with Avalon® -MM Input Interface and Avalon® -ST Output Interface figure below. The Avalon® -ST output (source) data width must also be 32 bits. You can configure output interface parameters, including: bits per symbol, symbols per beat, and the width of the channel and error signals. The FIFO core performs the endian conversion to conform to the output interface protocol.
The signals that comprise the output interface are mapped into bits in the Avalon® address space. If Allow backpressure is turned on, the input interface asserts waitrequest to indicate that the FIFO core does not have enough space for the transaction to complete.
Offset | 31 | 24 | 23 | 19 | 18 16 | 15 13 | 12 | 8 | 7 | 4 | 3 | 2 | 1 | 0 | ||||||||||||||||||
base + 0 | Symbol 3 | Symbol 2 | Symbol 1 | Symbol 0 | ||||||||||||||||||||||||||||
base + 1 | reserved | reserved | error | reserved | channel | reserved | empty | EOP | SOP |
Offset | Bits | Field | Description |
---|---|---|---|
0 | 31:0 | SYMBOL_0, SYMBOL_1, SYMBOL_2 .. SYMBOL_n | Packet data. The value of the Symbols per beat parameter specifies the number of fields in this register; Bits per symbol specifies the width of each field. |
1 | 0 | SOP | The value of the startofpacket signal. |
1 | EOP | The value of the endofpacket signal. | |
6:2 | EMPTY | The value of the empty signal. | |
7 | — | Reserved. | |
15:8 | CHANNEL | The value of the channel signal. The number of bits occupied corresponds to the width of the signal. For example, if the width of the channel signal is 5, bits 8 to 12 are occupied and bits 13 to 15 are unused. | |
23:16 | ERROR | The value of the error signal. The number of bits occupied corresponds to the width of the signal. For example, if the width of the error signal is 3, bits 16 to 18 are occupied and bits 19 to 23 are unused. | |
31:24 | — | Reserved. |
If Enable packet data is turned off, the Avalon® -MM write host writes all data at address offset 0 repeatedly to push data into the FIFO core.
If Enable packet data is turned on, the Avalon® -MM write host starts by writing the SOP, ERROR (optional), CHANNEL (optional), EOP, and EMPTY packet status information at address offset 1. Writing to address offset 1 does not push data into the FIFO core. The Avalon® -MM host then writes packet data to address offset 0 repeatedly, pushing 8-bit symbols into the FIFO core. Whenever a valid write occurs at address offset 0, the data and its respective packet information is pushed into the FIFO core. Subsequent data is written at address offset 0 without the need to clear the SOP field. Rewriting to address offset 1 is not required each time if the subsequent data to be pushed into the FIFO core is not the end-of-packet data, as long as ERROR and CHANNEL do not change.
At the end of each packet, the Avalon® -MM host writes to the address at offset 1 to set the EOP bit to 1, before writing the last symbol of the packet at offset 0. The write host uses the empty field to indicate the number of unused symbols at the end of the transfer. If the last packet data is not aligned with the symbols per beat, the EMPTY field indicates the number of empty symbols in the last packet data. For example, if the Avalon® -ST interface has symbols per beat of 4, and the last packet only has 3 symbols, the empty field will be 1, indicating that one symbol (the least significant symbol in the memory map) is empty.