SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
The Transfer Request Descriptor contains the following information:
Indicator which identifies the descriptor as a TR Descriptor
Set of one or more Transfer Request Records
Set of one or more Transfer Response Records
Transfer Request Packet Descriptors always contain 16 bytes of required information and a variable number of Transfer Request / Transfer Response Records (request and response counts match).
The Transfer Request descriptor layout is shown below.
Packet Info Given via Transfer Request Packet Descriptor Word 0-3 (16 bytes) |
Null (0-102 bytes to bring start of TR request array into natural alignment for memory fetch efficiency) |
Array of Transfer Request Records |
Array of Transfer Response Records |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:30 | 2’d3 | TR Packet Descriptor type. | No |
29 | RESERVED | No | |
28:20 | Reload Count | Specifies what to do when the last entry is processed in this packet. This field specifies how many times to return to the Reload Index upon reaching the Last Entry. When an internal count is incremented to this value and the TR indicated by the Last Entry has been processed, this packet will be considered complete and the descriptor will be placed back on the return queue specified in Word 2. A value of 0x1FF indicates that a perpetual loop is desired. In this case, the loop count is considered infinite and the internal count will not be incremented. A teardown operation on the channel will cause the loop to be broken at the nearest iteration boundary. | No |
19:14 | Reload Index | Specifies the value to set the current processing index to when the last entry is processed and the Reload Enable is set to 1. This is basically an absolute index to jump to on the 2nd and following passes through the TR packet. | No |
13:0 | Last Entry | Specifies the index of the last valid entry in this packet | No |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:28 | RESERVED | - | No |
27 | RESERVED | No | |
26:24 | Transfer Request Nominal Element Size | Specifies the stride between TR entries. The value in this field must be set large enough that any TR in the buffer will fit within the given dimension. TRs are expected to be placed on boundaries as given in this dimension. This field is also used to calculate the location where the Transfer Responses will be written back. This field is encoded as follows: 0 = 16-byte Transfer Request record size 1 = 32-byte Transfer Request record size 2 = 64-byte Transfer Request record size 3 = 128-byte Transfer Request record size 4-7 = RESERVED | No |
23:14 | RESERVED | - | No |
13:0 | RESERVED | - | No |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:17 | RESERVED | Yes | |
16 | RESERVED | - | Yes |
15:0 | RESERVED | - | Yes |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:24 | RESERVED | - | No |
15:0 | RESERVED | - | No |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:0 | Transfer Control Record Array | Transfer Control Records. This is an array of records which encapsulate the Transfer Request and Transfer Response messages which are used by the BCDMA | Yes (partial) |