DS21448 データシートの表示（PDF） - Maxim Integrated

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DS21448

3.3V E1/T1/J1 Quad Line Interface

Maxim Integrated 

DS21448 3.3V T1/E1/J1 Quad Line Interface

4. PORT OPERATION

4.1 Hardware Mode

The DS21448 supports a hardware configuration mode that allows the user to configure the device by setting levels

on the device’s pins. This mode allows the DS21448 configuration without the use of a microprocessor, simplifying

designs. Not all of the device features are supported in the hardware mode.

In hardware mode (BIS0 = 1, BIS1 = 1) several pins have been redefined so they can be used for initializing the

DS21448. Refer to Table 2-B and Table 2-E for pin assignment and definition. Because of limited pin count, several

functions have been combined and affect all four channels in the device and/or treat the receive and transmit paths

as one block. Restrictions when using the hardware mode include the following:

• BPCLK pins only output a 16.384MHz signal.

• The RCL/LOTC pins are designated to RCL.

• The RHBE and THBE control bits are combined and controlled by HBE.

• RSCLKE and TSCLKE bits are combined and controlled by SCLKE.

• TCES and RCES are combined and controlled by CES.

• The transmitter functions are combined and controlled by TX1 and TX0.

• Loopback functions are controlled by LOOP1 and LOOP0.

• JABDS defaults to 128-bit buffer depth.

• All other control bits default to logic 0.

Table 4-A. Loopback Control in Hardware Mode

LOOPBACK

Remote Loopback

Local Loopback

Analog Loopback

No Loopback

SYMBOL

RLB

LLB

ALB

—

LOOP1

1

1

0

0

LOOP0

1

0

1

0

Table 4-B. Transmit Data Control in Hardware Mode

TRANSMIT DATA

SYMBOL

TX1

TX0

Unframed All Ones

TUA1

1

1

Alternating Ones and Zeros

TAOZ

1

0

PRBS

TPRBSE

0

1

TPOS and TNEG

—

0

0

Table 4-C. Receive Sensitivity Settings in Hardware Mode

EGL

0

1

1

0

ETS

0 (E1)

0 (E1)

1 (T1)

1 (T1)

RECEIVE SENSITIVITY (dB)

-12 (short haul)

-43 (long haul)

-30 (limited long haul)

-36 (long haul)

Table 4-D. Monitor Gain Settings in Hardware Mode

MM1

0

0

1

1

MM0

0

1

0

1

INTERNAL LINEAR GAIN BOOST (dB)

Normal operation (no boost)

20

26

32

Table 4-E. Internal Rx Termination Select in Hardware Mode

RT1

RT0

0

0

0

1

1

0

1

1

INTERNAL RECEIVE

TERMINATION CONFIGURATION

Internal receive-side termination disabled

Internal receive-side 120Ω enabled

Internal receive-side 100Ω enabled

Internal receive-side 75Ω enabled

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