Preliminary Information

MT9123

8-47

4

ENB2

SSI Enable Strobe / ST-BUS Mode for Sin/Rout (Input). This pin has dual functions

depending on whether SSI or ST-BUS is selected.

For SSI, this is an active high channel enable strobe, 8 or 16 data bits wide, enabling serial

PCM data transfer for Echo Canceller B on Sin/Rout pins. Strobe period is 125 microseconds.

For ST-BUS, this pin, in conjunction with the ENA2 pin, will select the proper ST-BUS mode for

Sin/Rout pins (see ST-BUS Operation description). The selected mode applies to both Echo

Canceller A and B.

5

Rin

Receive PCM Signal Input (Input). 128 kbit/s to 4096 kbit/s serial PCM input stream. Data

may be in either companded or 2’s complement linear format. Two PCM channels are time-

multiplexed on this pin. These are the Receive Input reference channels for Echo Cancellers

A and B. Data bits are clocked in following SSI or ST-BUS timing requirements.

6

Sin

Send PCM Signal Input (Input). 128 kbit/s to 4096 kbit/s serial PCM input stream. Data may

be in either companded or 2’s complement linear format. Two PCM channels are time-

multiplexed on this pin. These are the Send Input channels (after echo path) for Echo

Cancellers A and B. Data bits are clocked in following SSI or ST-BUS timing requirements.

7

VSS

Digital Ground. Nominally 0 volts.

8

MCLK

Master Clock (Input). Nominal 20 MHz Master Clock input. May be connected to an

asynchronous (relative to frame signal) clock source.

9

IC1

Internal Connection 1 (Input). Must be tied to Vss.

10

NLP

Non-Linear Processor Control (Input).

Controllerless Mode: An active high enables the Non-Linear Processors in Echo Cancellers A

and B. Both NLP’s are disabled when low. Intended for conformance testing to G.165 and it is

usually tied to Vdd for normal operation.

Controller Mode: This pin is ignored (tie to Vdd or Vss). The non-linear processor operation is

controlled by the NLPDis bit in Control Register 2. Refer to the Register Summary.

11

IC2

Internal Connection 2 (Input). Must be tied to Vss.

12

LAW

A/

µ Law Select (Input). An active low selects µ−Law companded PCM. When high, selects

A-Law companded PCM. This control is for both echo cancellers and is valid for both

controller and controllerless modes.

13

FORMAT ITU-T/Sign Mag (Input). An active low selects sign-magnitude PCM code. When high,

selects ITU-T (G.711) PCM code. This control is for both echo cancellers and is valid for both

controller and controllerless modes.

14

PWRDN

Power-down (Input). An active low resets the device and puts the MT9123 into a low-power

stand-by mode.

15

IC3

Internal Connection 3 (Output). Must be left unconnected.

16

IC4

Internal Connection 4 (Output). Must be left unconnected.

17/18

17

18

S4/S3

SCLK

CS

Selection of Echo Canceller B Functional States (Input).

Controllerless Mode: Selects Echo Canceller B functional states according to Table 2.

Controller Mode: S4 and S3 pins become SCLK and CS pins respectively.

Serial Port Synchronous Clock (Input). Data clock for the serial microport interface.

Chip Select (Input). Enables serial microport interface data transfers. Active low.

Pin Description (continued)

Pin #

Name

Description