DS2155 datasheet(144/262 Pages) DALLAS

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DS2156

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22.3.3

FIFO Information

The transmit FIFO buffer-available register indicates the number of bytes that can be written into the

transmit FIFO. The count form this register informs the host as to how many bytes can be written into the

transmit FIFO without overflowing the buffer.

H1TFBA, H2TFBA

HDLC # 1 Transmit FIFO Buffer Available

HDLC # 2 Transmit FIFO Buffer Available

9Fh, Afh

Bit #

Name

TFBA7

TFBA6

TFBA5

TFBA4

TFBA3

TFBA2

TFBA1

TFBA0

Default

Bits 0 to 7/Transmit FIFO Bytes Available (TFBAO to TFBA7). TFBA0 is the LSB.

22.3.4

Receive Packet-Bytes Available

The lower 7 bits of the receive packet-bytes available register indicates the number of bytes (0 through

127) that can be read from the receive FIFO. The value indicated by this register (lower seven bits)

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 refers 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

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

message, then the MSB of the HxRPBA register returns a value of 1. This indicates that the host can

safely read the number of bytes returned by the lower seven bits of the HxRPBA register, but there is no

need to check the information register since the packet has not yet terminated (successfully or otherwise).

H1RPBA, H2RPBA

HDLC # 1 Receive Packet Bytes Available

HDLC # 2 Receive Packet Bytes Available

9Ch, ACh

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 INFO5 or

INFO6 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 INFO5 or INFO6 register.

DS2155 Datasheet(PDF) 144 Page - Dallas Semiconductor

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