Digi NS9750 - Manual (Page 736)

H o s t b l o c k
7 1 2 N S 9 7 5 0 H a r d w a r e R e f e r e n c e
Logical and physical endpoints
Each alternate of each interface of each configuration can use as many as 16 logical
endpoints. Physical endpoints in the device block are programmable by software for
configuration/interface/alternate number. type, direction, and
MaxPacketSize
. A
physical endpoint, then, functions as one logical endpoint in one alternate of one
interface of one configuration. The number of physical endpoints required is
therefore equal to the total number of logical endpoints in each alternate of each
interface of each configuration.
The device block is configured to hold 12 physical endpoints, endpoint 0, and 11 non-
control endpoints, with a maximum of 5 interfaces. This allows simultaneous
operation of the printer class, still image class, and three instances of the data class.
Programming of the physical endpoints and the descriptors provided allow you to
reassign any of the physical endpoints to any one of the five interfaces. A “multi-
function” fax/printer scanner device can take the place of three instances of the
data class if no more than six physical endpoints are required.
Slew rates
USB PHY has a greater than specified slew rate in low speed device mode. Faster slew
rates may cause compatibility issues with low speed hosts.
Host block
The USB host block contains the resources to implement an OHCI host. These
resources include a power control signal for USB port power. Figure 103 shows the
architecture for the USB host block.
Control and status
The control and status for the USB host block is provided using the slave interface.
The registers support the OHCI specification.