
XRT7250
DS3/E3 FRAMER IC
á
REV. 1.1.1
200
The bit-format of the Rx DS3 FEAC register is pre-
sented below. It is important to note that the last vali-
dated FEAC code word will be written into the shaded
bit-fields below.
The purpose of generating an interrupt to the P, up-
on FEAC Code Word Validation is to inform the local
P that the Framer has a newly received FEAC mes-
sage that needs to be read. The local P would read-
in this FEAC code word from the Rx DS3 FEAC Reg-
ister (Address = 0x16).
FEAC Code Removal
After the 10th transmission of a given FEAC code
word, the remote terminal equipment may proceed to
transmit a different FEAC code word. When the Re-
ceive FEAC processor detects this occurrence, it
must Remove the FEAC codeword that is presently
residing in the Rx DS3 FEAC Register. The Receive
FEAC Processor will remove the existing FEAC code
word when it detects that 3 (or more) out of the last
10 received FEAC codes are different from the latest
validated FEAC code word. The Receive FEAC Pro-
cessor will inform the local P/C of this removal
event by generating a Rx FEAC Removal interrupt,
and asserting the RxFEAC Remove Interrupt Status
bit in the Rx DS3 Interrupt Enable/Status Register, as
depicted below.
Additionally, the Receive FEAC processor will also
denote the removal event by setting the FEAC Valid
bit-field (Bit 4), within the Rx DS3 FEAC Interrupt En-
able/Status Register to 0, as depicted above.
The description of Bits 0 through 3 within this register,
all support Interrupt Processing, and will therefore be
presented in Section 3.3.6.
Figure 84 presents a flow
diagram depicting how the Receive FEAC Processor
functions.
RX DS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7BIT 6BIT 5
BIT 4BIT 3BIT2BIT 1
BIT 0
Not Used
FEAC
Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
R/W
RUR
R/W
RUR
XX
X
1X
0
1
RX DS3 FEAC REGISTER (ADDRESS = 0X16)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1BIT 0
Not Used
RxFEAC [5]
RxFEAC [4]
RxFEAC [3]
RxFEAC [2]
RxFEAC [1]
RxFEAC [0]
Not Used
RO
0
d5
d4
d3
d2
d1
d0
0
RX DS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7BIT 6BIT 5
BIT 4BIT 3
BIT2BIT 1BIT 0
Not Used
FEAC
Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
R/W
RUR
R/W
RUR
XX
X
01
1X0