User's Manual

1 Introduction and Description
MT5634ZPX-PCI 9
V.90 Support/Functions
V.90 is the ITU designation for what formerly was called V.pcm. V.90
replaces K56flex and other proprietary solutions for PCM connections.
Dual-mode client modem code will be important until all central-site
digital modems are upgraded to V.90 and all interoperability problems
are resolved. Until that time, the Dual-mode client code provides
reliable connections in K56flex mode to the central-site modems
currently deployed. V.90 functions/features include:
 V.90/K56flex A-law and µ-law support
 New downstream data rates (S-Register S38)
 Optional V.8bis sequence
 V.90 Mode Selection (S-Register S109) support
 Auto-rate speeds to 50,666 (downstream) support
 Automatic adapting to digital loss and robbed-bit signaling
 New V.90 rate result codes
Downstream Rates
Where K56flex provided rates of 32,000 to 56,000 in 2,000 bps
increments, V.90 provides rates of 28,000 to 56,000 bps in increments
of 1,333 bps.
Upstream Data Rates
Upstream V.90 data rates are 4800 to 33600 bps in 2400 bps
increments.
Optional V.8bis Sequence
The V.8bis sequence that precedes K56flex connections is optional for
V.90. Dual-mode servers indicate this capability using V.8bis. Dual-
mode clients complete the V.8bis exchange and then proceed to either
the K56flex mode or V.90 mode. V.90-only clients can skip the V.8bis
exchange as a way to shorten the startup time.
Auto-rate Speeds
Auto-rate speeds to 50,666 Kbps are supported for downstream
transfers.