isp1181 NXP Semiconductors, isp1181 Datasheet - Page 22

• Manufacturer Part Number: isp1181
• Description: Isp1181 Full-speed Universal Serial Bus Interface Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 08938
Product data
When external components are powered-off, it is possible that interface signals RD,
WR and CS have unknown values immediately after leaving ‘suspend’ state. To
prevent corruption of its internal registers, ISP1181 enables a locking mechanism
once suspend is enabled.
After wake-up from suspend’ state, all internal registers except the Unlock Register
are write-protected. A special unlock operation is needed to re-enable write access.
This prevents data corruption during power-up of external components.
Figure 8
powered-off mode. The SUSPEND output is used to switch off power to the
microcontroller and other external circuits during ‘suspend’ state. The ISP1181 is
woken up via the USB bus (global resume) or by the ring detection circuit on the
telephone line.
Fig 8. SUSPEND and WAKEUP signals in a powered-off modem application.
shows a typical bus-powered modem application using ISP1181 in
USB
Rev. 04 — 30 October 2001
V BUS
D
D
ISP1181
V CC
SUSPEND
WAKEUP
power
switch
RING DETECTION
V CC
CONTROLLER
© Koninklijke Philips Electronics N.V. 2001. All rights reserved.
MICRO-
Full-speed USB interface
MGS783
ISP1181
LINE
22 of 71