TAS1020A Datasheet, PDF (16/114 Pages) Texas Instruments – USB Streaming Controller

2.1.6 USB Buffer Manager (UBM)
The USB buffer manager provides the control logic that interfaces the SIE to the USB endpoint buffers. One of the
major functions of the UBM is to decode the USB function address to determine if the host PC is addressing the
TAS1020A device USB peripheral function. In addition, the endpoint address field and direction signal are decoded
to determine which particular USB endpoint is being addressed. Based on the direction of the USB transaction and
the endpoint number, the UBM will either write or read the data packet to or from the appropriate USB endpoint data
buffer.
2.1.7 USB Frame Timer
The USB frame timer logic receives the start of frame (SOF) packet from the host PC each USB frame. Each frame,
the logic stores the 11-bit frame number value from the SOF packet in a register and asserts the internal SOF signal.
The frame number register can be read by the MCU and the value can be used as a time stamp. For USB frames
in which the SOF packet is corrupted or not received, the frame timer logic will generate a pseudo start of frame
(PSOF) signal and increment the frame number register.
2.1.8 USB Suspend and Resume Logic
The USB suspend and resume logic detects suspend and resume conditions on the USB. This logic also provides
the internal signals used to control the TAS1020A device when these conditions occur. The capability to resume
operation from a suspend condition with a locally generated remote wake-up event is also provided.
2.1.9 MCU Core
The TAS1020A uses an 8-bit microcontroller core that is based on the industry standard 8052. The MCU is software
compatible with the 8052, 8032, 80C52, 80C53, and 87C52 MCUs. The 8052 MCU is the processing core of the
TAS1020A and handles all USB control, interrupt and bulk endpoint transfers. Bulk out end-point transfers can also
be handled by one of the two DMA channels.
2.1.10 MCU Memory
In accordance with the industry standard 8052, the TAS1020A MCU memory is organized into program memory,
external data memory and internal data memory. A boot ROM program is used to download the application code to
a 6K byte RAM that is mapped to the program memory space. The external data memory includes the USB endpoint
configuration blocks, USB data buffers, and memory mapped registers. The total external data memory space
available is 1.5K bytes. A total of 256 bytes are provided for the internal data memory.
2.1.11 USB Endpoint Configuration Blocks and Buffer Space
The USB endpoint configuration blocks are used by the MCU to configure and operate the required USB endpoints
for a particular application. In addition to the control end-point, the TAS1020A supports a total of seven IN endpoints
and seven OUT endpoints. A set of six bytes is provided for each endpoint to specify the endpoint type, buffer address,
buffer size, and data packet byte count.
The USB endpoint buffer configuration blocks and buffer space provided totals 1440 bytes. The buffer space to be
used by a particular endpoint is fully configurable by the MCU for a particular application. Therefore, the MCU can
configure each buffer based on the total number of endpoints to be used, the maximum packet size to be used for
each endpoint, and the selection of single or double buffering.
2.1.12 DMA Controller
Two DMA channels are provided to support the streaming of data for USB isochronous IN endpoints, isochronous
OUT endpoints, and bulk OUT endpoints. Each DMA channel can support one USB isochronous IN endpoint, or one
isochronous OUT endpoint, or one bulk OUT endpoint. The DMA channels are used to stream data between the USB
2–2