XRT72L50 Datasheet, PDF (462/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
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RxE3 Interrupt Status Register - 2 (Address = 0x15)
BIT 7
Not Used
RO
0
BIT 6
TTB
Change
Interrupt
Status
RUR
0
BIT 5
Not Used
RO
0
BIT 4
FEBE
Interrupt
Status
RUR
0
BIT 3
FERF
Interrupt
Status
RUR
0
BIT 2
BIP-8
Error Interrupt
Status
RUR
0
BIT 1
Framing
Byte Error
Interrupt
Status
RUR
0
BIT 0
RxPld
Mis
Interrupt
Status
RUR
1
6.3.6.2.12 The Receive LAPD Message Interrupt
If the Receive LAPD Message Interrupt is enabled, then the XRT72L50 Framer IC will generate an interrupt
anytime the Receive HDLC Controller block has received a new LAPD Message frame from the Remote
Terminal Equipment, and has stored the contents of this message into the Receive LAPD Message buffer.
Enabling/Disabling the Receive LAPD Message Interrupt
The user can enable or disable the Receive LAPD Message Interrupt by writing the appropriate data into Bit 1
(RxLAPD Interrupt Enable) within the Rx E3 LAPD Control Register, as indicated below.
RxE3 LAPD Control Register (Address = 0x18)
BIT 7
RO
0
BIT 6
BIT 5
Not Used
RO
RO
0
0
BIT 4
RO
0
BIT 3
DL from NR
BIT 2
RxLAPD
Enable
R/W
R/W
0
0
BIT 1
RxLAPD
Interrupt
Enable
R/W
0
BIT 0
RxLAPD
Interrupt
Status
RUR
X
Writing a “1” into this bit-field enables the Receive LAPD Message Interrupt. Conversely, writing a “0” into this
bit-field disables the Receive LAPD Message Interrupt.
Servicing the Receive LAPD Message Interrupt
Whenever the XRT72L50 Framer IC generates this interrupt, it will do the following.
• It will assert the Interrupt Request output pin (Int), by driving it "Low".
• It will set Bit 0 (RxLAPD Interrupt Status), within the Rx E3 LAPD Control register to “1”, as indicated below.
RxE3 LAPD Control Register (Address = 0x18)
BIT 7
RO
0
BIT 6
BIT 5
Not Used
RO
RO
0
0
BIT 4
RO
0
BIT 3
DL from NR
BIT 2
RxLAPD
Enable
R/W
R/W
0
0
BIT 1
RxLAPD
Interrupt
Enable
R/W
1
BIT 0
RxLAPD
Interrupt
Status
RUR
1
• It will write the contents of the newly Received LAPD Message into the Receive LAPD Message buffer
(located at 0xDE through 0x135).
Whenever the Terminal Equipment encounters the Receive LAPD Message Interrupt, then it should read out
the contents of the Receive LAPD Message buffer, and respond accordingly.
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