MT8931C
The C-channel bit mapping from the parallel port to
the ST-BUS is organized such that the most
significant bit is transmitted or received first.
State Activation
The state activation controller activates or
deactivates the SNIC in response to line activity or
external command. The controller is completely
hardware driven and need not be initialized by the
microprocessor. The state diagram for initialization
is shown in Figure 7.
The protocol used by the state activation controller is
defined as follows:
1) In the deactivated state, neither the NT nor TE
assert a signal on the line (Info0).
2) If the TE wants to initiate activation, it must begin
transmitting a continuous signal consisting of a
positive zero, a negative zero followed by six
ones (Info1).
3) Once the NT has detected Info1, it begins to
transmit Info2 which consists of an S-Bus frame
Signals from NT to TE
Info0
No Signal
Info0
Info1
Signals from TE to NT
No Signal
Continuous Signal of +‘0’, -‘0’
and six ‘1’s
(1)
Where: BA
(2)
= Bus Activity
DR = Deactivation Request
AR = Activation Request
Sync
(2)
= Frame Sync Signal
A = Activation bit
Time out = 32 ms Timer Signal
Note 1: signal is not timebase locked to NT.
Info2
Valid frame structure with
all B, D, D-echo and A bits
set to ‘0’
Info3
Valid frame with data in B,
D, D-echo channels. Bit A is
set to 1.
Valid frame with data in B & D
Bits
Info4
Note 2: Sync/BA bit of the Status Register
is configured as Sync bit when
AR = 1 and DR = 0, or as BA bit
when AR = 0 or DR = 1. A change in
the state of the AR and/or DR bits
will cause a change in the function
of the Sync/BA bit in the following
ST-BUS frame.
TE State Activation Diagram
DR = 1
AR = 1
BA = 0
Deactivated
send Info0
Sync = 1
DR = 1
DR = 1
Activated
send Info3
A=1&
Sync = 1
Sync = 0
A=0
BA = 0
NT State Activation Diagram
BA = 1
AR = 1
DR = 1
Pending
Activation
send Info2
Sync = 1
DR = 1
Sync = 0
Activated
send Info4
Pending
Deactivation
Send Info0
Deactivated
send Info0
Time out
BA =0
Synchronized
send Info3 if Sync = 1
send Info0 if Sync = 0
Activation Request
send Info1 if BA = 0
send Info0 if BA = 1
Sync = 1
AR = 1
Figure 7 - Link Activation Protocol, State Diagram
9-78
MITEL [ MITEL NETWORKS CORPORATION ]
