Advance Information
MT9074
Bit
Name
Functional Description
Bit
Name
Functional Description
1
RXFF
RX FIFO Full. This bit is set when
the Rx FIFO is filled above the
selected full threshold level. This
bit is reset after a read.
7
GA
Go Ahead. Indicates a go-ahead
pattern was detected by the HDLC
receiver. This bit is reset after a
read.
0
RxOVF RX FIFO Overflow. Indicates that
the 128 byte RX FIFO overflowed
(i.e. an attempt to write to a 128
byte full RX FIFO). The HDLC will
always disable the receiver once
the receive overflow has been
detected. The receiver will be re-
enabled upon detection of the next
flag, but will overflow again unless
the RX FIFO is read. This bit is
reset after a read.
6
RxEOP End Of Packet Detected. This bit
is set when an end of packet
(EOP) byte was written into the RX
FIFO by the HDLC receiver. This
can be in the form of a flag, an
abort sequence or as an invalid
packet. This bit is reset after a
read.
5
4
TxEOP Transmit End Of Packet. This bit
is set when the transmitter has
finished sending the closing flag of
a packet or after a packet has
been aborted. This bit is reset after
read.
Table 148 - HDLC Interrupt Status Register
(Page B & C, Address 17H)
RxFE
End Of Packet Read. This bit is
set when the byte about to be read
from the RX FIFO is the last byte of
the packet. It is also set if the Rx
FIFO is read and there is no data in
it. This bit is reset after a read.
Bit Name
Functional Description
7-0 CRC1 The MSB byte of the CRC received
5-8 from the transmitter. These bits are
as the transmitter sent them; that is,
most significant bit first and inverted.
This register is updated at the end of
each received packet and therefore
should be read when end of packet is
detected.
3
2
TXFL
FA:
TX FIFO Low. This bit is set when
the Tx FIFO is emptied below the
selected low threshold level. This
bit is reset after a read.
Table 149 - Receive CRC MSB Register
(Page B & C, Address 18H)
Frame Abort/TX FIFO Under-
TxUND run.When Intsel bit of Control Reg-
ER
ister 2 is low, this bit (FA) is set
when a frame abort is received dur-
ing packet reception. It must be re-
ceived after a minimum number of
bits have been received (26) other-
wise it is ignored.
Bit Name
Functional Description
7-0 CRC7-0 The LSB byte of the CRC received
from the transmitter. These bits
are as the transmitter sent them;
that is, most significant bit first and
inverted. This register is updated at
the end of each received packet and
therefore should be read when end
of packet is detected.
When INTSEL bit of Control
Register 2 is high, this bit is set for
a TX FIFO underrun indication. If
high it Indicates that a read by the
transmitter was attempted on an
empty Tx FIFO.
This bit is reset after a read.
Table 148 - HDLC Interrupt Status Register
(Page B & C, Address 17H)
Table 150 - Receive CRC LSB Register
(Page B & C, Address 19H)
103
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