MT90812AP datasheet(46/105 Pages) MITEL

46 / 105 page

MT90812

Advance Information

The second condition occurs if the Auto-hunt circuit manages to cycle back to monitor a peripheral which is

already the currently active receive channel. Because the peripheral continues to

send request-to-sends

during the time when it is being acknowledged with a go-ahead from the RX circuitry, it is important that ﬂags

not be detected twice for the same request. This condition is prevented by disabling scanning on a currently

active receive channel.

The third condition that causes the Auto-hunt circuit to skip a channel, is if it has been locked out by the

system. This allows the system to independently disable reception from any channel. On reset, all 16 D-

channels are locked out, and the system must specify which channels are to be enabled for receive activity.

The two HDLC CTRL Lockout registers are described in Section 22.30 and Section 22.31.

The fourth condition that will cause the Auto-hunt circuit to skip a channel occurs when the scanned-channel

number is the same as an active TX channel. The channel is skipped in this case to reduce the contention

between a system transmit packet and the transmission of a CTS. If a ﬂag has been detected before the

transmitter goes active on the same channel, then the contention, described in “TX and RX Handshaking” on

page 38, will occur. However, if the transmitter goes active at any point before a ﬂag is detected, then

contention will be avoided.

14.1.7

Receive Packet Termination

A receive packet will be terminated when the HDLC controller asserts the REOP strobe for one bit period, one

bit time after the closing ﬂag is received. If desired, the system may assert its own SREOP ﬂag via the micro

interface. The SREOP bit is in “HRA CTRL Register 2 (HC2)” on page 71. This ﬂag has the same effect as the

normal REOP strobe, but may be written asynchronously and will be cleared by the RX circuit after it has been

acted upon. In either case, a receive end-of-packet will cause RXACT to go low, disabling RxCEN.

15.0 C-Channel Data

C-Channel access for Codec or DNIC control is provided through Message Mode (refer to “Connection

Memory” on page 10). The C-Channel information can be read from Data Memory or written to Connect

Memory.

C-Channel data status information is very static. Therefore, the interface as provided via Message Mode is

single buffered. Hence, the C-channel information may change every frame.

16.0 Tone Generation

The MT90812 generates the standard 16 DTMF frequencies within +/- 0.6% of the nominal standard

frequencies. Table 13 shows the standard DTMF frequencies, the coefﬁcient used to generate the closest

frequency, the actual frequency generated and the percent deviation of the generated tone from the nominal.

Table 13 - DTMF Frequencies

Tone

Group

Frequency Hz

Coefﬁcient

Actual Frequency

% Deviation

Low

697

59H

695.31

-0.24%

770

62H

765.63

-0.56%

852

6DH

851.56

-0.05%

941

78H

937.50

-0.37%

High

1209

8DH

1203.12

-0.49%

1336

96H

1343.75

+0.58%

1477

9FH

1484.38

+0.50%

1633

A9H

1640.62

+0.47%

MT90812AP Datasheet(PDF) 46 Page - Mitel Networks Corporation

MT90812AP Datasheet(HTML) 46 Page - Mitel Networks Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL