EZ-USB FX3 Technical Reference Manual, Document Number: 001-76074 Rev. *F 620
DSCR_SIZE
0x02C
10.25.10 DSCR_SIZE
Descriptor Size Register
The error and start/end of packet markers are provided by the IP through hardware signals when streaming data into the
socket. These signal are optional and are used only for IP that can produce packets larger than on buffer and/or IP that can
detect errors and produce meaningful packets in these cases.
Only eop,byte_count,error,buffer_occupied are modified by the adapter after the initial read from memory. This is the only reg-
ister that is written back into memory by the adapter. This register is not intended to be modified by software directly.
31:16 BYTE_COUNT[15:0] The number of data bytes present in the buffer. An occupied buffer is not always full, in particular
when variable length packets are transferred.
15:4 BUFFER_SIZE[11:0] The size of the buffer in multiples of 16 bytes
3 BUFFER_OCCUPIED Indicates the buffer is in use (1) or empty (0). A consumer will interpret this as:
0 Buffer is empty, wait until filled.
1 Buffer has data that can be consumed
A producer will interpret this as:
0 Buffer is ready to be filled
1 Buffer is occupied, wait until empty
2 BUFFER_ERROR Indicates the buffer data is valid (0) or in error (1).
continued on next page
DSCR_SIZE Descriptor Size Register 0x02C
b31 b30 b29 b28 b27 b26 b25 b24
BYTE_COUNT[15:8]
R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
XXXXXXXX
DSCR_SIZE Descriptor Size Register
b23 b22 b21 b20 b19 b18 b17 b16
BYTE_COUNT[7:0]
R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
XXXXXXXX
DSCR_SIZE Descriptor Size Register
b15 b14 b13 b12 b11 b10 b9 b8
BUFFER_SIZE[11:4]
R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
XXXXXXXX
DSCR_SIZE Descriptor Size Register
b7 b6 b5 b4 b3 b2 b1 b0
BUFFER_SIZE[3:0]
BUFFER_
OCCUPIED
BUFFER_ERROR EOP MARKER
R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
XXXXXXXX
Bit Name Description
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