DS26401 datasheet(202/309 Pages) DALLAS

202 / 309 page

DS26401 Octal T1/E1/J1 Framer

202

10.16.2 Receive Packet Bytes Available

The lower 6 bits of the Receive Packet Bytes Available register indicates the number of bytes (0 through 64) that

can be read from the receive FIFO. The value indicated by this register informs the host as to how many bytes can

be read from the receive FIFO without going past the end of a message. This value will refer to one of four

possibilities, the first part of a packet, the continuation of a packet, the last part of a packet, or a complete packet.

After reading the number of bytes indicated by this register the host then checks the HDLC Status register for

detailed message status.

If the value in the RHPBA register refers to the beginning portion of a message or continuation of a message then

the MSB of the RHPBA register will return a value of 1. This indicates that the host may safely read the number of

bytes returned by the lower 6 bits of the RHPBA register but there is no need to check the information register since

the packet has not yet terminated (successfully or otherwise).

RHPBA

Receive HDLC Packet Bytes Available Register

0B5h + (200h x n) : where n = 0 to 7, for Ports 1 to 8

Bit #

Name

RPBA6

RPBA5

RPBA4

RPBA3

RPBA2

RPBA1

RPBA0

Default

Bits 0 to 6 / Receive FIFO Packet Bytes Available Count (RPBA0 to RPBA6).

RPBA0 is the LSB.

Bit 7 / Message Status (MS)

0 = Bytes indicated by RPBA0 through RPBA6 are the end of a message. Host must check the HDLC

Status register for details.

1 = Bytes indicated by RPBA0 through RPBA6 are the beginning or continuation of a message. The host

does not need to check the HDLC Status.

DS26401 Datasheet(PDF) 202 Page - Dallas Semiconductor