Chapter 3 — Theory of Operation
CV30 Fixed Mount Computer Service Manual 73
USB Hub
The USB Hub ISP 1520 is a standalone controller that complies with the
USB Specification 2.0. It supports data transfer at high speed (480 Mbps),
full speed (12 Mbps), and low speed (1.5 Mbps). The processor is limited
to full speed, therefore the controller will operate as a full speed device.
USB Hub Block Diagram
The hub is protected by the external over-current switch MIC2026, which
is connected through the digital over current signal nUSBOC1/2 to the
hub. The protection can be configured as individual port control or
ganged-port control depending on the pin PSWn_N configuration.
Signal Description
USBH_DPn Downstream USB line positive
USBH_DMn Downstream USB line negative
USBH_P0 Upstream USB line positive
USBH_N0 Upstream USB line negative
USBH_RESET Hub RESET, controlled by processor
nUSBOCn Over current sense input
nUSB_PSWn Power switch control output
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