
Preliminary Information
MT9071
63
10.2.1
E1 CAS Register and ST-BUS Access
For CAS operation, the signaling bit enable control register bit CSIG (see Table 85 - E1 DL, CCS, CAS and
Other Control - R/W Address Y03) must be set to zero.
Access to the ABCD transmit and receive bits may be either through ST-BUS channels 1 to 15 and channels 17
to 31 at the CSTi and CSTo pins, or through transmit data registers (see Table 163 - E1 Transmit CAS Data
Registers - R/W Address Y51-Y5F & Y61-Y6F) and receive data registers (see Table 165 - E1 Receive CAS
Data Registers - R Address Y71-Y7F, Y81-Y8F) accessed by the parallel processor port, or through a mix of
both methods.
The timeslot control register bits CASS(1-15,17-31) (see Table 167 - E1 Per Timeslot 0 to 31 Control Registers
- R/W Address Y90-YAF) determine the source of the CAS data on a per channel basis. If zero, the transmit
signaling information is constantly updated with the information from the equivalent channel on CSTi, if one,
the transmit CAS data register is the source. Note that when changing the CASS(1-15,17-31) timeslot control
register bits from ST-BUS source to register source on the fly (during normal operation as opposed to during
power up), the transmit CAS data registers are updated one frame after the timeslot control register bits are
changed. This is because the timeslot control register bits do not take effect immediately. Both destinations of
CAS data are always enabled (i.e. ST-BUS CSTo and receive CAS data registers). The receive signaling bits
are always mapped to the equivalent ST-BUS channels on CSTo (see Table 21 - E1 CAS & ST-BUS CSTi/CSTo
Timeslot Relationship).
CAS
Frame
PCM30 Timeslot 16
1
2
3
4
5
6
7
8
Channel
Associated
Signaling
(CAS)
Multiframe
(not related
to CRC-4
multiframing)
0
1
2
3
4
5
6
7
8
9
0000 (MAS)
ABCD (ch 1 = ts1)
ABCD (ch 2 = ts 2)
ABCD (ch 3 = ts 3)
ABCD (ch 4 = ts 4)
ABCD (ch 5 = ts 5)
ABCD (ch 6 = ts 6)
ABCD (ch 7 = ts 7)
ABCD (ch 8 = ts 8)
ABCD (ch 9 = ts 9)
ABCD (ch 10 = ts 10)
ABCD (ch 11 = ts 11)
ABCD (ch 12 = ts 12)
ABCD (ch 13 = ts 13)
ABCD (ch 14 = ts 14)
ABCD (ch 15 = ts 15)
XYXX (NMAS)
ABCD (ch 16 = ts 17)
ABCD (ch 17 = ts 18)
ABCD (ch 18 = ts 19)
ABCD (ch 19 = ts 20)
ABCD (ch 20 = ts 21)
ABCD (ch 21 = ts 22)
ABCD (ch 22 = ts 23)
ABCD (ch 23 = ts 24)
ABCD (ch 24 = ts 25)
ABCD (ch 25 = ts 26)
ABCD (ch 26 = ts 27)
ABCD (ch 27 = ts 28)
ABCD (ch 28 = ts 29)
ABCD (ch 29 = ts 30)
ABCD (ch 30 = ts 31)
10
11
12
13
14
15
Table 20 - E1 CAS Multiframe Structure
MAS - Multiframe Alignment Signal
NMAS - Non-Multiframe Alignment Signal
X - Spare Bit = 1 if not used
Y - Remote Multiframe Alarm Signal