T7256 Agere Systems, T7256 Datasheet - Page 19

• Manufacturer Part Number: T7256
• Description: (T7234 - T7256) Compliance
• Manufacturer: Agere Systems

Lucent Technologies Inc.
February 1998
STLED Description
The STLED pin is used to drive an LED and provides a
visual indication of the current state of the T7234. The
STLED control is typically configured to illuminate the
LED when STLED is LOW. This convention will be
assumed throughout this section.
Table 4 describes the four states of STLED, the list of
system conditions that produce the state, and the cor-
responding ANSI states, as defined in ANSI T1.601-
1992 (Tables C1 and C4) and ETSI ETR 080-1992
(Tables A3 and I2).
Table 4. STLED States
*
† State H8(a) is most likely when U-interface bit uoa = 0.
High (LED off)
8 Hz Flashing
1 Hz Flashing
Low (LED on)
These are ETSI DTR/TM-3002 states not yet defined in ANSI T1.601, although they are defined in revised ANSI tables which are currently on
the living list (i.e., not yet an official part of the standards document).
STLED State
RESET (pin 43) = 0
AUTOCTL = 0 or
AUTOEOC = 0 or
STOA = 0
U and S/T not active
RESET = 0
Quiet mode active, or
ILOSS mode active
U activation attempt in progress
AIB = 0
eoc-initiated 2B+D loopback active
U active, S/T not fully active
U and S/T fully active
List of System Conditions that
Can Cause STLED State
T7234 Single-Chip NT1 (SCNT1) Euro-LITE Transceiver
Note:
The flow chart in Figure 10 illustrates the priority of the
logic signals which control the STLED pin. Note that
quiet mode and ILOSS mode are ANSI maintenance
modes, and aib is a U-interface overhead bit.
The ETSI state names begin with the letters
NT instead of H. Also, the ETSI state tables
do not include a state NT11 because it is con-
sidered identical to state NT6. Table A3 of the
ETSI standard contains the additional states
NT6A, NT7A, and NT8A to describe state
related to the eoc loopback 2 (2B+D loop-
back). The most likely ANSI state for each
STLED state is shown in bold typeface, in
Table 4.
NA
H0, H1, H10, H12
NA
H7, H8
H8
Corresponding ANSI States
H2, H3, H4
NT6A*, NT7A*, NT8A*
H6, H6(a), H7, H11, H8(a)
H8(b), H8(c)
†
,
15