PM6344 datasheet(212/256 Pages) PMC

212 / 256 page

STANDARD PRODUCT

PMC-Sierra, Inc.

PM6344 EQUAD

PMC-951013

ISSUE 5

QUADRUPLE E1 FRAMER

199

output low. The FIFO buffer is not cleared when an abort is detected. All bytes

received up to the abort are available to be read.

After an abort, the RFDL state machine will be in the receiving all ones state,

and the data link status will be idle. When the first flag is detected, a new

interrupt will be generated, with a dummy data byte loaded into the FIFO buffer,

to indicate that the data link is now active.

Figure 25

- RFDL FIFO Overrun

Serial Data

extracted from

ESF FDL

RDLINT[x]

RDLEOM[x]

D[7:0]

Flag

R C1

Flag

B2 B3

STATUSRD

Dn-1

OVR

R Abort

This diagram shows the relationship between RFDL inputs and outputs for the

case where interrupts are programmed to occur when two data bytes are present

in the FIFO buffer. Each read is composed of two register reads, as described

above. In this example, data is not read by the end of B2. An overrun occurs

since unread data (Dn-3) has been overwritten by B1. This sets the RDLEOM[x]

output high, and resets both the RFDL and the FIFO buffer. The RFDL is held

disabled until the RFDL Status Register is read. The start flag sequence is not

detected since the RFDL is still held disabled when it occurs. Consequently, the

RFDL will ignore the entire frame including the abort sequence (since it has not

occurred in a valid frame or during flag reception, according to the RFDL).

PM6344 Datasheet(PDF) 212 Page - PMC-Sierra, Inc