TP3420AV datasheet(15/32 Pages) NSC

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Functional Description (Continued)

MULTIFRAME TRANSMIT AND RECEIVE REGISTERS

MFT1L)

MFT1H)

MFT2)

MFR1)

MFR2)

MIE1)

MID1)

MID2)

With the device in TE Mode, data entered in

M1, M2, M3 and M4 bits of MTF1L is

transmitted towards the NT in multiframe bit

positions Q1, Q2, Q3 and Q4 respectively.

With the device in NT Mode, data entered

(via MFT1L, MFT1H) in the M bit positions is

transmitted towards the TE in multiframe bit

positions S11, S12, S13 and S14

respectively. Data entered via MFT2

command in the M bit positions is

transmitted in multiframe bit positions S21,

S22, S23, S24 respectively. The Multiframe

Channel and Interrupts (MFR1, MFR2) must

be enabled by the MIE1, MIE2 to use these

channels. The MID1, MID2 commands will

disable the interrupts MFR1, MFR2 (and in

NT mode only, it will also disable the

multiframing clock to the TEs). See also the

section on Multiframe Maintenance Channel.

MULTIFRAME MESSAGE REPETITION AND

VALIDATION

MFC1E)

MFC6E)

MFC1D)

MFC6D)

These commands control the frequency of

the MFC Interrupt that is used as an aid to

the software to transmit multiframe

commands. If both MFC1E and MFC6E

commands are set, then the MFC Interrupt

will occur every multiframe (5 ms). The

interrupt may be disabled with MFC1D,

MFC6D. The MFC6E command also enables

the internal 6 multiframe counter that

ensures that every MFT1L command is sent

for 6 consecutive multiframes before sending

another command loaded in the MFT1L

internal 6 multiframe counter. See also the

section on Multiframe Maintenance Channel.

ENINT

This command enables the RMFE and SLIP

interrupts and thus accesses new features of

TP3420A.

DISINT

Disables RMFE and SLIP interrupts.

ENV)

DISV)

ENV enables the 3-times validation of certain

SC1/Q and SC2 channel messages (Table

8) before generating the MFR1 and MFR2

interrupt respectively. DISV disables this

circuit so that the MFR1 and MFR2

interrupts are generated whenever there is a

change in the received multiframe word in

either channel.

ENST)

DISST)

ENST enables the state of the internal

Activation State machine to be reported to

the microcontroller by the NOCST response

to any MICROWIRE command thereafter.

The DISST causes the NOCST to be

replaced by the normal NOC status. See the

section on Activation State machine access.

PINDEF

This command is used to choose alternate

pin functions on Pins 8 and 18. Please see

Table 1 for the selection values.

ACTIVATION STATE MACHINE ACCESS

The TP3420A has a mechanism which allows the microcon-

troller to read the internal activation state of the chip. The MI-

CROWIRE command ENST (Enable Status) X’92 enables

the device state information to be output as a MICROWIRE

status word NOCST (1,S3,S2,S1,0,0,0,0) in response to any

subsequent MICROWIRE command. However, if a state

change interrupt occurs, e.g., an AP (Activation Pending)

then the interrupt status value is returned, otherwise the

NOCST status is returned. See

Table 6 below to relate the

values of the S3, S2, S1 bits to internal activation state of the

device.

TABLE 6. TP3420A Activation State Table

G1.1

G1.2

—

100

—

101

—

110

A clean way of monitoring the device state is to write a ENST

command, followed immediately by a DISST (Disable Sta-

tus) command. The NOCST status returned at the end of the

DISST contains the actual state of the device. Subsequent

MICROWIRE commands will be responded by NOC

(0,0,0,0,0,0,0,0). This method makes it easy for the software

to keep track of when to expect the device state via the

NOCST.

Another method would be to repeat the NOP command a

couple of times after a ENST command and observe that the

device state information (through the NOCST) is repeated to

be sure of the state of the device.

IDENTIFYING A TP3420A FROM A TP3420 DEVICE

The TP3420A on power-up default is functionally compatible

with a TP3420 device, and hence software written for a

TP3420 is applicable for a TP3420A device. Additional de-

vice features may be invoked by MICROWIRE commands. A

simple way of identifying a TP3420A from a TP3420 is as fol-

lows:

Upon application of power, write ENST followed by DISST

MICROWIRE commands to the device and evaluate the

NOCST status word. If the device is a TP3420A the value

should be 1000000, indicating the device is in F1/G0 state. A

TP3420 device will ignore the ENST/DISST commands and

return the normal NOC (00000000) status back.

MAINTENANCE LOOPBACKS

The TP3420A supports all the ANSI T1.605 and I.430 loop-

back modes and some additional loopback modes to allow

greater flexibility in performing fault isolation.

B1 digital loopback (using LBB1 command) with any

FSa/FSb relationship in all TE or NT modes.

B2 digital loopback (LBB2) with any FSa/FSb relation-

ship in all TE or NT modes.

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