MT9173/74

Preliminary Information

9-148

Table 4a. Default Mode Selection

Notes:

Table 5. Diagnostic Register

Notes:

Œ

When bits 4-7 of the Diagnostic Register are all set to one, the DNIC operates in one of the default modes as defined in Table 4a,

depending upon the status of bit-3.



Ž

Do not use DSTo to DSTi loopback in MOD/MAS mode.

C-Channel

(Bit 0-7)

Internal Control

Register

Internal Diagnostic

Register

Description

XXX01111

00000000

01000000

Default Mode-1

PSEN, DINB, DRR and all diagnostics are disabled.

TxHK=0.

XXX11111

00010000

01000000

Default Mode-2

PSEN, DINB, DRR and all diagnostics are disabled.

TxHK=0.

Bit

Name

Description

0

Reg Sel-1

Register Select-1. Must be set to ’0’ to select the Diagnostic Register.

1

Reg Sel-2

Register Select-2. Must be set to ’1’ to select the Diagnostic Register.

2,3

Loopback

Bit 2

Bit 3

0

0

All loopback testing functions disabled. Normal operation.

0

1

DSTi internally looped back into DSTo for system diagnostics.

10



1

1

DSTo is internally looped back into DSTi for end-to-end testing.

Ž

4

FUN

Œ

Force Unsync. When set to ’1’, the DNIC is forced out-of-sync to test the SYNC

recovery circuitry. When set to ’0’, the operation continues in synchronization.

5

PSWAP

Œ

Polynomial Swap. When set to ’1’, the scrambling and descrambling polynomials

are interchanged (use for MAS mode only). When set to ’0’, the polynomials retain

their normal designations.

6

DLO

Œ

7

Not Used

Must be set to ’0’ for normal operation.

bit 0

bit 1

bit 2

bit 3

bit 4

bit 5

bit 6

bit 7

Reg Sel-1

Reg Sel-2

Loopback

FUN

PSWAP

DLO

Not Used

Default Mode Selection

(Refer to Table 4a)

The Diagnostics Register Reset bit (bit 2) of the

Control Register determines the reset state of the

Diagnostics Register. If, on writing to the Control

Register, this bit is set to logic “0”, the Diagnostics

Register will be reset coincident with the frame

pulse. When this bit is logic “1”, the Diagnostics

Register will not be reset.

In order to use the

diagnostic features, the Diagnostics Register must

be continuously written to. The output C-channel

sends status information from the Status Register to

the system along with the received HK bit as shown

in Table 6.

In MOD mode, the CD port is no longer an ST-BUS

but is a serial bit stream operating at the bit rate

selected. It continues to transfer the C-channel but

the D-channel and the HK bit no longer exist. DUAL

port operation must be used in MOD mode. The C-

channel is clocked in and out of the CD port by TCK

and CLD with TCK defining the bits and CLD the