Isochronous Out Transaction - Epson S2R72V18 Technical Manual

1. Functions
1.4.3.4

Isochronous OUT Transaction

The transfer type (H_CHx{x=b-e}Config_1.TranType) is set to "Isochronous," and the transaction
type (H_CHx{x=b-e}Config_1.TID) is set to "OUT" for the CHx{x=b-e} basic setting register. The
token-issuing interval (H_CHx{x=b-e}Interval_H,L), other basic settings, and then transfer
execution (H_CHx{x=b-e}Config_0.TranGo) are set appropriately, subjecting the channel to
hardware-based USB transfer scheduling. The token-issuing interval (H_CHx{x=b-e}Interval_H,L),
valid FIFO data quantity, and remaining frame time are determined when scheduling selects the
corresponding channels, and an isochronous OUT transaction is executed.
The data packet length is the smaller of H_CHx{x=b-e}MaxPacketSize_H,L and
H_CHx{x=b-e}TotalSize_HH,HL,LH,LL.
An ACK status notification (H_CHx{x=b-e}IntStat.TranACK bit) is issued to the firmware once
the isochronous OUT transaction ends. The FIFO is then updated, freeing the area by treating the
data sent as already sent.
A transaction is not sent if the valid FIFO data quantity is less than the data packet data length.
Therefore, the FIFO is not updated, and the area is not freed. TranErr status is issued to the
firmware and the condition code (H_CHx{x=b-e}ConditionCode) is set to "BufferUnderrun."
Fig. 1-27 shows the configuration for an isochronous OUT transaction when completed. (a) The LSI
issues an OUT token addressed to the OUT-direction endpoint at the destination node. (b) The LSI
then sends a data packet no larger than the maximum packet size. The LSI automatically sets the
corresponding register after sending the data packet, and issues status information to the firmware.
60
OUT
a
Fig. 1-27 Isochronous OUT transaction
EPSON
DATA
b
Host to Device
Device to Host
S2R72V18 Technical Manual (Rev.1.00)