Information Technology Reference
In-Depth Information
after sending the requested quantity of data, the device may stall the bulk
IN endpoint.
If a device expects to receive a different quantity of data than the host
specified in the CBW, the device may stall the bulk OUT endpoint.
If a device determinines that it can't complete a command during the
data-transport phase, the device may stall the bulk IN or bulk OUT end-
point as appropriate.
The thirteen cases described below have more about the use of STALL with
mass-storage commands.
Thirteen Cases for Any Situation
The mass-storage bulk-only transport specification spells out how the host
and device should behave after the host sends a command in each of thirteen
cases. Cases 1, 6, and 12 (in bold) are the normal cases, where the host and
device each expect the same quantity and direction of data transfer in the
data-transport phase. The other cases are situations where the host and
device have differing expectations.
1. The host expects no data-transport phase.
The device expects no data-transport phase.
2. The host expects no data-transport phase.
The device expects to send data.
3. The host expects no data-transport phase.
The device expects to receive data.
4. The host expects to receive data.
The device expects no data-transport phase.
5. The host expects to receive data.
The device expects to send less data than the host intends to receive.
6. The host expects to receive data.
The device expects to send the exact amount of data the host
intends to receive.
7.
The host expects to receive data.
The device intends to send more data than the host expects to receive.
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