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R01UH0823EJ0100 Rev.1.00
Page 955 of 1823
Jul 31, 2019
RX23W Group
32. USB 2.0 Host/Function Module (USBc)
32.3.11
Pipe Schedule
32.3.11.1
Conditions for Generating a Transaction
When the host controller is selected and the DVSTCTR0.UACT bit has been set to 1, the USB generates a transaction
under the conditions shown in
Note 1. Symbols (—) in the table indicate that the condition is unrelated to the generating of tokens. "Valid" indicates that, for interrupt
transfers and isochronous transfers, a transaction is generated only in transfer frames that are based on the interval counter.
"Invalid" indicates that a transaction is generated regardless of the interval counter.
Note 2. This indicates that a transaction is generated regardless of whether there is a receive area. If there is no receive area, however,
the received data is discarded.
Note 3. This indicates that a transaction is generated regardless of whether there is any data to be transmitted. If there is no data to be
transmitted, however, a zero-length packet is transmitted.
32.3.11.2
Transfer Schedule
This section describes the transfer scheduling within a frame of the USB. After the USB sends an SOF, the transfer is
carried out in the sequence described below.
1. Execution of periodic transfers
A pipe is searched in the order of PIPE1 → PIPE2 → PIPE6 → PIPE7 → PIPE8 → PIPE9, and then, if there is a
pipe for which an isochronous or interrupt transfer transaction can be generated, the transaction is generated.
2. Setup transactions for control transfers
The DCP is checked, and if a setup transaction is possible, it is sent.
3. Execution of bulk transfers, control transfer data stages, and control transfer status stages
A pipe is searched in the order of DCP → PIPE1 → PIPE2 → PIPE3 → PIPE4 → PIPE5, and then, if there is a pipe
for which a transaction for a bulk transfer, a control transfer data stage, or a control transfer status stage can be
generated, the transaction is generated.
When a transaction is generated, processing moves to the next pipe transaction regardless of whether the response
from the peripheral device is ACK or NAK. If there is time for transfer within the frame, step 3 is repeated.
32.3.11.3
Enabling USB Communication
Setting the DVSTCTR0.UACT bit to 1 initiates SOF transmission and transaction generation is enabled.
Setting the UACT bit to 0 stops SOF transmission and a suspend state is entered. If the setting of the UACT bit is
changed from 1 to 0, processing stops after the next SOF is sent.
Table 32.25
Conditions for Generating a Transaction
Transaction
Conditions for Generation
DIR
PID[1:0]
IITV[0]
Buffer State
SUREQ
Setup
—*
1 setting
Control transfer data stage, status stage,
bulk transfer
IN
BUF
Invalid
Receive area
exists
OUT
BUF
Invalid
Transmit data
exists
Interrupt transfer
IN
BUF
Valid
Receive area
exists
OUT
BUF
Valid
Transmit data
exists
Isochronous transfer
IN
BUF
Valid
OUT
BUF
Valid