HD6417727BP160CV Datasheet, PDF (817/1098 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family/ SH7700 Series

Section 24 USB HOST Module
24.4.2 Restriction on the Memory Access Address
MPS in ED, CBP in General TD, and BP0 and OFFSET0 to 7 in Ischoronous TD must be set in
multiples of 4 (4n). In the OpenHCI standard, 1 packet is transferred by ITD in General TD and 1
packet by 1 offset in Ischronous TD. In addition, when the amount of the data specified by TD
during OUT transfer exceeds MAXPACKETSIZE (MPS), a packet transmission is carried out in
MAXPACKETSIZE. Therefore, the setting value can be made as above. This restriction is due to
the difference between the specifications of the HCI interface which is the standard of the IP bus
interface of USB and of the bus interface of SH7727. Data might be correctly written to if data is
transferred from addresses other than 4n address. For example, when a two-byte transfer is carried
out from the address that terminates at 1, a long-word transfer is carried out and an unexpected
data is written to starting address 0.
24.5 Restrictions on the Data Transfer of USB Controller
24.5.1 Restriction of the Data Size in IN Transfer
When a data packet shorter than MAXPACKETSIZE (short packet) is transferred in the IN data
transfer, following usages are restricted.
1. Usage when a dribble bit is added
When HUB are connected in multiple steps, a dribble bit may be added at the end of the
packet.
2. When receiving the data with final 6 bits in CRC are all 1 (in this case, bit stuffing occurs)
In this case, this USB controller may write IN data in the memory with one byte additionally.
Therefore, usage of 1 is prohibited. In usage of 2, the software must be written to so that no
problem occurs even additional data of 1 byte is written to. In concrete, in the usage to connect
the received short packets are connected in the memory, 1 byte of unnecessary data might be
inserted. Be sure to transfer MAXPACKETSIZE mainly and the processed data will be used so
that the end of the data or head can be recognized when a short packet is sent. In applications
where the receive data size cannot be controlled by software, it is not possible to use software
to remove the 1 byte of unnecessary data. When using the module in such cases, appropriate
countermeasures must be considered.
24.5.2 Restrictions on the Hub Connection on NAK/STALL Reception
When NAK or STALL is received as a handshake from the USB function module, the following
usage is restricted.
1. Usage where a dribble bit is added
Rev.6.00 Mar. 27, 2009 Page 759 of 1036
REJ09B0254-0600