PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 298

• Manufacturer Part Number: PEF2091
• Description: ICs for Communications(ISDN Echocancellation Circuit)
• Manufacturer: Siemens Semiconductor Group

PEB 2091
PEF 2091
Appendix B Comment on Activation in µP-NT Modes
Erroneous Signals on U-Interface after Power-Up in NT Mode with Enabled
Microprocessor Interface Mode
This point applies only if the IEC-Q is used in NT mode and if the microprocessor
interface mode is enabled by pin PMODE set to "1". The stand-alone mode is not
affected.
After applying V
(power-on) the device enters the LT mode according to the default
DD
value C4
in the STCR register (see "STCR-Register", page 212). In applications where
H
®
no IOM
-2 clocks are provided to the PEB/F 2091 Version 5.1 this results in an
undefined state of the IEC-Q. The undefined state may cause unwanted signals on the
U-interface. It is left once the device is brought into the NT or TE mode by programming
the STCR register. Thus, for the time between applying V
and programming the STCR
DD
register, unwanted signals may be sent on the U-interface.
In the PSB/F 21911 IEC-Q TE the default value of the STCR register has been changed
to "04H". Thus "unwanted" signals won’t be sent on the U-interface any longer.
Semiconductor Group
298
Data Sheet 01.99