CD2481 Datasheet, PDF (169/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

Programmable Four-Channel Communications Controller — CD2481
the receiver buffer and/or FIFO. The OE status is set on the last character received
before the overrun occurred.
Bit 2
Parity error
This bit indicates that a parity error occurred on this character.
Bit 1
Reserved; returns ‘0’ when read.
Bit 0
Lead change
This bit indicates a change of state on the CTS* pin from the previous character time.
Because there is no character sync during some phases of the X.21 call setup, an
Lchg indication can precede a special character interrupt.
Note: During an interrupt service routine, the host can use this register to provide a timer value as
detailed in the Receive End of Interrupt register. The host can only load one of the two timers in the
interrupt service routine.
RISRl – Async-HDLC / PPP / MNP4 Mode
Register Name: RISRl
Register Description: Receive Interrupt Status Register - Low
Default Value: x’00
Access: Byte Read Only
Bit 7
Bit 6
Bit 5
Bit 4
0
EOF
RxAbt
CRC
Bit 3
OE
Intel Hex Address: x’8A
Motorola Hex Address: x’89
Bit 2
FE
Bit 1
0
Bit 0
Break
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Binary Value for Timer
Bit 2
Bit 1
Bit 0
If RxData in IER is set, these interrupts are enabled.
Bit 7
Reserved; returns ‘0’ when read.
Bit 6
EOF – End of frame
The EOF bit indicates that a valid end of frame (7E) character has been received, and
the 7E was not preceded by a 7D.
Bit 5
rxabt – Receive abort
The rxabt bit indicates that an abort sequence (7D–7E) has been received.
Bit 4
CRC – Receive CRC error
(The terms CRC and FCS are used interchangeably in this document.)
The CRC bit indicates that a frame with a valid end of frame has been received, but
the FCS was not correct. CRC is set only if EOF is set.
Bit 3
OE – Overrun error
The OE bit indicates that the receiver buffer and FIFO have been overrun. At least
one new character has been received, but lost since there was no room available in
the receiver buffer and/or FIFO.
Datasheet
169