33781 datasheet(39/44 Pages) FREESCALE

39 / 44 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

33781

FUNCTIONAL DEVICE OPERATION

PROTECTION AND DIAGNOSTIC FEATURES

nodes to charge. In the case of DLY changing, any partial

inter-frame delay based on old control settings is lost.

ENABLE (DISABLE) FUNCTION

When a DBUS channel is disabled, the 33781 device

forces its bus output to tri-state. When the channel is disabled

the channel addressed buffer data bits are cleared, the status

reset. Any DBUS transfer that was in progress is stopped.

CHANNEL LOOP FUNCTION

When loop mode is enabled the transmitter and receiver

circuits are connected within the IC. This allows data to be

passed directly through the transmit and receive circuits

without going out on the DBUS channel. When LOOP mode

is enabled the DBUS channel is disconnected from the

transmitter and receiver circuits so that any bus fault

conditions do not interfere with this test. When the loop

function is enabled, the EN bit in the DnEN register is cleared,

the buffer data bits are cleared, the status register bits are

reset, and the transmit and receive queue reset the by the

state machine. When the loop mode is exited the state

machine sets the registers to their reset state and resets the

transmit and receive queue. This allows proper start up of bus

transactions.

The channel queue pointers work the same as in non-loop

mode.

33781 Fiches technique(PDF) 39 Page - Freescale Semiconductor, Inc