Datasheet

8−15
SLLS535E − April 2008 TUSB6250
Table 8−4 shows the buffer location address map for a single buffer with a buffer size of 64 bytes.
Table 8−4. EDB0 Buffer Locations (in SPRAM)
ADDRESS NAME DESCRIPTION
EFFF
TOPBUFF
Top of buffer space
↑
|
|
|
|
|
↓
TOPBUFF
Buffer space
4K – 128 bytes free
E080
E07F ↑
↑
|
↓
64 bytes
I
Input endpoint_0, buffer
I
E040 ↓
E03F
↑
↑
|
↓
64 bytes
↑
I
Output endpoint_0, buffer
|
E000
|
↓
NOTE: This table is based on a single buffer with a buffer size of 64 bytes
for both input and output endpoint-0.
8.10 Endpoint Descriptor Block (EDB-1 to EDB-4)
The endpoint descriptor block (EDB) defines the endpoint characteristics for data transfer between the USB
and the UBM. Four input and four output endpoints are provided. All EDBs are implemented in
memory-mapped registers as defined in Table 6−2.
Double data buffers are provided for EDB-1 to EDB-4 (both input and output endpoints). The firmware in the
MCU decides whether to use the double data buffers by writing to the DBUF bit in the IEPCNFG_n and
OEPCNFG_n registers. The double data buffer is disabled by default (DBUF = 0). In this case, only the primary
data buffer (X-buffer) is enabled.
Each EDB contains information describing the X and Y-buffers. In addition, it provides general status
information. Figure 8−2 and Figure 8−3 illustrate how the IN_Endpoint_number (E[2:0]) and
OUT_Endpoint_number (E[2:0]) are used to generate the index (address) to the input EDB and the output
EDB, respectively, in the MMR memory map. Note that A[3] is used to distinguish between input and output.
Table 8−5 illustrates each EDB entry (register) for EDB-1 to EDB-4.
Figure 8−4 illustrates how the complete 16-bit EDB-buffer base address within the MMR memory map is
generated in the TUSB6250 hardware for each EDB data buffer.
As defined in the USB 2.0 specification, the maximum packet size is 512 bytes for a high-speed bulk endpoint
and 64 bytes for a full-speed bulk endpoint.
Endpoint # IN
Bit Value 1 1 1 1 0 0 0 0 0 E2 E1 E0 0 0 0 0
Bit Number A15 A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
Figure 8−2. IN-Endpoint Index Generation