ISP1760ET,557 NXP Semiconductors, ISP1760ET,557 Datasheet - Page 17

• Manufacturer Part Number: ISP1760ET,557
• Manufacturer: NXP Semiconductors

Specifications of ISP1760ET,557

• Package Type: TFBGA
• Pin Count: 128
• Lead Free Status / RoHS Status: Compliant

NXP Semiconductors
ISP1760_4
Product data sheet
7.2.2 Structure of the ISP1760 host controller memory
A larger buffer also implies a larger amount of data can be transferred. The transfer,
however, can be done over a longer period of time, to maintain the overall system
performance. Each transfer of the USB data on the USB bus can span for up to a few
milliseconds before requiring further CPU intervention for data movement.
The internal architecture of the ISP1760 allows a flexible definition of the memory buffer
for optimization of the data transfer on the CPU extension bus and the USB. It is possible
to implement various data transfer schemes, depending on the number and type of USB
devices present. For example: push-pull; data can be written to half of the memory while
data in the other half is being accessed by the host controller and sent on the USB bus.
This is useful especially when a high-bandwidth ‘continuous or periodic’ data flow is
required.
Through an analysis of the hardware and software environment regarding the usual data
flow and performance requirements of most embedded systems, NXP has determined the
optimal size for the internal buffer as approximately 64 kB.
The 63 kB internal memory consists of the PTD area and the payload area.
PTD memory zone is divided into three dedicated areas for each main type of USB
transfer: Isochronous (ISO), Interrupt (INT) and Asynchronous Transfer List (ATL). As
shown in
memory, occupying the address range 0400h to 0FFFh, following the register address
space. The payload or data area occupies the next memory address range 1000h to
FFFFh, meaning that 60 kB of memory are allocated for the payload data.
A maximum of 32 PTD areas and their allocated payload areas can be defined for each
type of transfer. The structure of a PTD is similar for every transfer type and consists of
eight Double Words (DWs) that must be correctly programmed for a correct USB data
transfer. The reserved bits of a PTD must be set to logic 0. A detailed description of the
PTD structure can be found in
The transfer size specified by the PTD determines the contiguous USB data transfer that
can be performed without any CPU intervention. The respective payload memory area
must be equal to the transfer size defined. The maximum transfer size is flexible and can
be optimized, depending on the number and nature of USB devices or PTDs defined and
their respective MaxPacketSize.
The CPU will program the DMA to transfer the necessary data in the payload memory.
The next CPU intervention will be required only when the current transfer is completed
and DMA programming is necessary to transfer the next data payload. This is normally
signaled by the IRQ that is generated by the ISP1760 on completing the current PTD,
meaning all the data in the payload area was sent on the USB bus. The external IRQ
signal is asserted according to the settings in the IRQ Mask OR or IRQ Mask AND
registers, see
The RAM is structured in blocks of PTDs and payloads so that while the USB is executing
on an active transfer-based PTD, the processor can simultaneously fill up another block
area in the RAM. A PTD and its payload can then be updated on-the-fly without stopping
or delaying any other USB transaction or corrupting the RAM data.
Some of the design features are:
Table
Section
4, the PTD areas for ISO, INT and ATL are grouped at the beginning of the
Rev. 04 — 4 February 2008
8.4.
Section
9.
Embedded Hi-Speed USB host controller
© NXP B.V. 2008. All rights reserved.
ISP1760
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