CMOS MT88E43：兼容多标准的电话身份识别电路

需积分: 18 200 浏览量更新于2024-08-02 收藏 318KB PDF 举报

CMOS MT88E43是一款高度集成的电路模块，专为电信行业的各种应用设计，特别是与英国电信(BT)的SIN227和SIN242标准、英国电缆通信协会(CCA)的TW/P&E/312规范以及贝尔核心(Bellcore)的GR-30-CORE（前身为TR-NWT-000030）和SR-TSV-002476标准兼容。该电路的核心功能包括： 1. **兼容性**：支持多种通信系统，如BT的Calling Line Identity Presentation (CLIP) 和 CCACLIP，以及贝尔核心的Calling Identity Delivery (CID) 系统，确保了广泛的设备兼容。 2. **呼叫号码识别**：能够检测并解析各种信号，如Bellcore的"CPE Alerting Signal (CAS)" 和 BT的"Idle State Tone Alert Signal"，用于确认来电者的身份或网络状态。 3. **音频处理**：具备1200 baud Bell 202和CCITT V.23 Frequency Shift Keying (FSK) 解调能力，适用于语音通信和数据传输。 4. **电源管理**：工作在3.58 MHz晶体振荡器下，提供3到5伏特±10%的电压范围，且具有低功耗特性，支持电源下电模式，有利于电池供电设备的续航。 5. **接口灵活性**：支持3-wire数据接口，可以由微控制器或MT88E43本身控制，适应不同应用场景下的连接需求。 6. **高灵敏度输入**：拥有高输入灵敏度，-40分贝V Tone和FSK检测能力，确保即使在噪声环境中也能准确捕获信号。 7. **附加功能**：内置输入增益可调放大器，提供carrier detect status输出，便于外部设备监控通信状态。 8. **广泛应用领域**：广泛应用于电话交换机、功能电话（包括ADSI电话）、电话机附件盒、传真机、答录机以及数据库查询和计算机电话集成(CTI)系统等，满足不同场景下的用户需求。 CMOS MT88E43电路以其多功能性、低功耗和广泛的兼容性，在电信和通信行业中扮演着关键角色，为各类终端设备提供了高效、可靠的呼叫号码识别和音频信号处理能力。

Data Sheet

MT88E43

5-57

2. Ring Burst Detection

CCA does not support the dual tone alert signal

(refer to Dual Tone Alert Signal Detection section).

Instead, CCA requires that the TE be able to detect a

single burst of ringing (duration 200-450ms) that

precedes CLIP FSK data. The ring burst may vary

from 30 to 75Vrms and is approximately 25Hz.

Again in a TE designed for CCA CLIP, the TRIGout

high to low transition may be used to interrupt or

wake-up the microcontroller. The controller can thus

be put into power-down mode to conserve power in a

battery operated TE.

3. Ring Detection

In Bellcore’s CND/CNAM scheme, the CID FSK data

is transmitted between the first and second ringing

cycles. The circuit in Figure 3 will generate a ring

envelope signal (active low) at TRIGout for a ring

voltage of at least 40Vrms. R5 and C3 filter the ring

signal to provide an envelope output.

The diode bridge shown in Figure 3 works for both

single ended and balanced ringing. A fraction of the

ring voltage is applied to the TRIGin input. When the

voltage at TRIGin is above the Schmitt trigger high

going threshold V

T+

, TRIGRC is pulled low as C3

discharges. TRIGout stays low as long as the C3

voltage stays below the minimum V

T+

In a CPE designed for CND/CNAM, the TRIGout

high to low transition may be used to interrupt or

wake-up the microcontroller. The controller can thus

be put into power-down mode to conserve power.

If precise ring duration determination is critical,

capacitor C3 in Figure 3 may be removed. The

microcontroller will now be able to time the ring

duration directly. The result will be that TRIGout will

be low only as long as the ringing signal is present.

Previously the RC time constant would cause only

one interrupt.

Dual Tone Alert Signal Detection

The BT on hook (idle state) caller ID scheme uses a

dual tone alert signal whose characteristics are

shown in Table 1.

Bellcore specifies a similar dual tone alert signal

called CPE Alerting Signal (CAS) for use in off-hook

data transmission (see Table 1). Bellcore states that

the CPE should be able to detect the CAS in the

presence of near end speech. The CAS detector

should also be immune to imitation from near and far

end speech.

In the MT88E43 the dual tone alert signal is

separated into a high and a low tone by two

bandpass filters. A detection algorithm examines the

two filter outputs to determine the presence of a dual

tone alert signal. The ESt pin goes high when both

tones are present. Note that ESt is only a preliminary

indication. The indication must be sustained over the

tone present guard time to be considered valid. Tone

present and tone absent guard times can be

implemented with external RC components. The

tone present guard time rejects signals of insufficient

duration. The tone absent guard time masks

momentary detection dropout once the present

guard time has been satisfied. StD is the guard time

qualified detector output.

Item BT Bellcore

Low tone

frequency

2130Hz ±1.1% 2130Hz ±0.5%

High tone

frequency

2750Hz ± 1.1% 2750Hz ± 0.5%

Received

signal level

-2dBV to -40dBV

per tone on-hook

(0.22dBm

-37.78dBm)

a. In the future BT may specify the off-hook signal level as

-15dBm to -34dBm per tone for BT CIDCW.

b. The signal power is expressed in dBm referenced to 600 ohm

at the CPE A/B (tip/ring) interface.

-14dBm

- 32dBm per tone

off-hook

Signal reject

level

-46dBV

(-43.78dBm)

-45dBm

Signal level

differential

(twist)

up to 7dB up to 6dB

Unwanted

signals

<= -20dB

(300-3400Hz)

<= -7dBm ASL

near end speech

c. ASL = active speech level expressed in dBm referenced to

600 ohm at the CPE tip/ring interface. The level is measured

according to method B of Recommendation P.56 "Objective

Measurement of Active Speech Level" published in the CCITT

Blue Book, volume V "Telephone Transmission Quality" 1989.

EPL (Equivalent Peak Level) = ASL+11.7dB

Duration 88ms to 110ms

d. SIN227 suggests that the recognition time should be not less

than 20ms if both tones are detected.

75ms to 85ms

Speech

present

No Yes

Table 1 - Dual Tone Alert Signal

Characteristics

MT88E43

Preliminary Information

5-58

Dual Tone Detection Guard Time

When the dual tone alert signal is detected by the

MT88E43, ESt goes high. When the alerting signal

ceases to be detected, ESt goes low.

The ESt pin signals raw detection of CAS/Alerting

Tones. Since both Bellcore and BT applications

require a minimum duration for valid signals, ESt

detection must be guard time qualified. The StD pin

provides guard time qualified CAS/Alerting Tone

detection. When the MT88E43 is used in a caller

identity system, StD indicates correct CAS/Alerting

Tone detection.

Figure 4 shows the relationship between the St/GT,

ESt and StD pins. It also shows the operation of a

guard time circuit.

The total recognition time is t

REC

= t

+ t

, where

is the tone present guard time and t

is the tone

present detect time (refer to timing between ESt, St/

GT and StD in Figures 17 and 20).

The total tone absent time is t

ABS

= t

+ t

, where

is the tone absent guard time and t

is the tone

absent detect time (refer to timing between ESt, St/

GT and StD in Figures 17 and 20).

Bellcore states that it is desirable to be able to turn

off CAS detection for an off-hook capable CPE. The

disable switch allows the subscriber who

disconnects a service that relies on CAS detection

(e.g., CIDCW) but retains the CPE, to turn off the

detector and not be bothered by false detection.

When SW1 in Figure 4 is in the B position the guard

time circuit is disabled. The detector will still process

CAS/Alerting tones but the MT88E43 will not signal

their presence by ensuring StD is low.

BT specifies that the idle state tone alert signal

recognition time should not be less than 20ms when

both tones are used for detection. That is, both tones

must be detected together for at least 20ms before

the signal can be declared valid. This requirement

can be met by setting the t

(refer to Figure 5) to at

least 20ms.

BT also specifies that the TE is required to apply a

D.C. wetting pulse and an AC load 15-25ms after the

end of the alerting signal. If t

ABS

is 15 to

25ms, the D.C. current wetting pulse and the A.C.

load can both be applied at the falling edge of StD.

The maximum t

is 8ms so t

should be 15-17ms.

Therefore, t

must be greater than t

. Figure 5(a)

shows a possible implementation. The values in

Figures 9 and 11 (R2=R3=422K, C=0.1µF) will meet

the BT timing requirements.

Figure 4 - Guard Time Circuit Operation

Figure 5 - Guard Time Circuits with

Unequal Times

Input Configuration

The MT88E43 provides an input arrangement

comprised of an operational amplifier and a bias

source (V

Ref

); which is used to bias the opamp inputs

at V

/2. The feedback resistor at the opamp output

(GS) can be used to adjust the gain. In a single-

ended configuration, the opamp is connected as

shown in Figure 6. For a differential input

configuration, Figure 7 shows the necessary

connections.

TGt

ESt

St/GT

StD

= V

Tones detected

From

MT88E43

Comparator

SW1

detector

(b) t

< t

= R

C ln [V

-V

/R2))/(V

-V

TGt

-V

/R2))]

= R1C ln (V

TGt

)

= R1R2/(R1+R2)

(a) t

> t

= R1C ln [V

/(V

-V

TGt

)]

= R

C ln [(V

-V

/R2))/(V

TGt

-V

/R2))]

= R1R2/(R1+R2)

MT88E43

St/GT

ESt

St/GT

ESt

R1 R2

MT88E43

=diode forward voltage

剩余25页未读，继续阅读

happy1231

粉丝: 10
资源: 64

CMOS MT88E43：兼容多标准的电话身份识别电路

联想E43的BIOS 0dcn82ww

xp系统下昭阳E43A更新BIOS程序

K43&E43 Maker

E43Y450.rar

E43 移印机.rar

溯高美E43X电表说明书

E43 移印机 shom.zip

联想K43_E43_XPEngerycut 热键驱动

联想E43A驱动包.rar

昭阳E43A1000M网卡XP驱动

最新资源