STLC5465B datasheet(42/101 Pages) STMICROELECTRONICS

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III - FUNCTIONAL DESCRIPTION (continued)

LOW P ASS

F ILTER

VCXO

f = 15 360kHz

or 16384kHz

VCXO IN

VCXO OUT

EVM

MHDLC

Re f =

409 6kHz

if f = 153 60kHz, p = 30

if f = 163 84kHz, p = 32

OUX

Figure 32 : VCXO Frequency Synchronization

III.8 - Interrupt Controller

III.8.1 - Description

Three external pins are used to manage the inter-

rupts generated by the

Multi-HDLC. The interrupts

have three main sources :

- The operating interrupts generated by the HDLC

receivers/transmitters, the CI receivers and the

monitor transmitters/receivers. INT0 Pin is re-

served for this use.

- The interrupt generatedby an abnormal working of

theclockdistribution.INT1Pinis reservedforthisuse.

- The non-activity of the microprocessor (Watch-

dog). WDO Pin is reserved for this use.

III.8.2 - Operating Interrupts (INT0 Pin)

There are five main sources of operating interrupts

in the

Multi-HDLC circuit :

- The HDLC receiver,

- The HDLC transmitter,

- The CI receiver,

- The Monitor receiver,

- The Monitor transmitter.

When an interrupt is generated by one of these

functions, the interrupt controller :

- Collects all the information about the reasons of

this interrupt,

- Stores them in external memory,

- Informs the microprocessor by positioning the

INT0 pin in the high level.

Three interrupt queues are built in external memory

to store the information about the interrupts :

- A single queue for the HDLC receivers and trans-

mitters,

- One for the CI receivers,

- One for the monitor receivers.

The microprocessor takes the interrupts into ac-

count by reading the Interrupt Register (IR) of the

interrupt controller.

This register informs the microprocessor of the

interrupt source. The microprocessor will have in-

formation about the interrupt source by readingthe

corresponding interrupt queue (see Paragraph ”In-

terrupt Register IR (38)H” on Page 91).

On an overflow of the circular interrupt queues and

an overrun or underrun of the different FIFO, the

INT0 Pin is activated and the origin of the interrupt

is stored in the Interrupt Register.

A 16 bits register is associated with the Tx Monitor

interrupt. It informs the microprocessor of which

transmitter has generated the interrupt (see Para-

graph ”Transmit Monitor Interrupt Register TMIR

(30)H” on Page 88).

III.8.3 - Time Base Interrupts (INT1 Pin)

The Time base interrupt is generated when an

absence or an abnormal working of clock distribu-

tion is detected. The INT1 Pin is activated.

III.8.4 - Emergency Interrupts (WDO Pin)

The WDO signal is activated by an overflow of the

watchdog register.

III.8.5 - Interrupt Queues

There are three different interrupt queues :

- Tx and Rx HDLC interrupt queue,

- Rx C/I interrupt queue,

- Rx Monitor interrupt queue.

Their length can be defined by software.

For debugging function, each interrupt word of the

CI interrupt queue and monitor interrupt queue can

be followed by a timestamped word. It is composed

of a counter which runs in the range of 250

µs. The

counter is the same as the watchdog counter.

Consequently,the watchdog functionisn’t available

at the same time.

STLC5465B

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