Hitachi H8S/2215 Series, Hardware Manual

Page: 585 / 745

Rev. 3.0, 10/02, page 527 of 686
15.9.7 EP3o Isochronous Transfer
•
Reception of EP3o data larger than the maximum packet size
The EP3o data FIFO cannot receive data with size larger than the maximum packet size; the
excessive data is lost. In this case, the receive size register
3o
(UESZ3o) can count up to the
maximum packet size and the EP3o abnormal transfer flag (EP3oTF) is set to 1.
Figure 15.31 shows the 10-byte data reception when the maximum packet size is specified as 9
bytes.
Data (1)
Data (2)
Data (3)
Data (4)
Data (5)
Data (6)
Data (7)
Data (8)
Data (9)
Data (10)
Count up to maximum
packet size
Data storage
Set the EP3o abnormal
transfer flag
EP3o FIFO
UESZ3o
H'09
Store data items within the
maximum packet size
Exessive data items are lost
Data (1)
Data (2)
Data (3)
Data (4)
Data (5)
Data (6)
Data (7)
Data (8)
Data (9)
UIFR1/EP3oTF
1
Figure 15.31 10-Byte Data Reception
•
EP3o receive data and status bit reading
As shown in figure 15.32, FIFO are switched on SOF packet reception. FIFOs thus store the
latest data. Accordingly, receive data sent from the host in frame [N] can only be read in frame
[N+1]. In addition, the EP3oTF and EP3oTS status bits of UIFR1 are automatically switched
on with each SOF packet reception; the EP3oTF and EP3oTS status in frame [N] can only be
read in frame [N+1].