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Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Product data sheet
Rev. 01 — 12 January 2005
16 of 158
Philips Semiconductors
ISP1761
Hi-Speed USB OTG controller
Port 2 does not need to be enabled using software if only port 1 or port 3 is used. No port
needs to be disabled by external pull-up resistors, if not used. The DP and DM of the
unused ports need not be externally pulled HIGH because there are internal pull-down
resistors on each port that are enabled by default.
Table 3
lists the various port connection scenarios.
7.2 Host Controller buffer memory block
7.2.1
General considerations
The internal addressable Host Controller buffer memory is 63 kB. The 63 kB effective
memory size is the result of subtracting the size of registers (1 kB) from the total
addressable memory space defined by the ISP1761 (64 kB). This is an optimized value
for achieving the highest performance with a minimal cost.
The ISP1761 is a slave Host Controller. This means that it does not need access to the
local bus of the system to transfer data from the memory of the system to the ISP1761
internal memory, unlike the case of the original PCI Hi-Speed USB Host Controllers.
Therefore, correct data must be transferred to both the Philips Transfer Descriptor (PTD)
area and the payload area by Parallel I/O (PIO) (CPU access) or programmed DMA.
The ‘slave-host’ architecture ensures better compatibility with most of the processors
present in the market today because not all processors allow a ‘bus-master’ on the local
bus. It also allows better load balancing of the processor’s local bus because only the
internal bus arbiter of the processor controls the transfer of data dedicated to USB. This
prevents the local bus from being busy when other more important transfers may be in the
queue; and therefore achieving a ‘linear’ system data flow that has less impact on other
processes running at the same time.
The considerations mentioned are also the main reason for implementing the prefetching
technique, instead of using a READY signal. The resulting architecture avoids ‘freezing’ of
the local bus (by asserting READY), enhancing the ISP1761 memory access time, and
avoiding introduction of programmed additional wait states. For details, see
Section 7.3
.
Table 3:
Port configuration Port 1
One port (port 1)
Port connection scenarios
Port 2
DP and DM are not connected
(left open)
DP and DM are routed to USB
connector
DP and DM are not connected
(left open)
DP and DM are routed to USB
connector
DP and DM are routed to USB
connector
DP and DM are not connected
(left open)
DP and DM are routed to USB
connector
Port 3
DP and DM are not connected
(left open)
DP and DM are not connected
(left open)
DP and DM are routed to USB
connector
DP and DM are not connected
(left open)
DP and DM are routed to USB
connector
DP and DM are routed to USB
connector
DP and DM are routed to USB
connector
DP and DM are routed to USB
connector
DP and DM are not connected
(left open)
DP and DM are not connected
(left open)
DP and DM are routed to USB
connector
DP and DM are not connected
(left open)
DP and DM are routed to USB
connector
DP and DM are routed to USB
connector
One port (port 2)
One port (port 3)
Two ports
(ports 1 and 2)
Two ports
(ports 2 and 3)
Two ports
(ports 1 and 3)
Three ports
(ports 1, 2 and 3)