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PRELIMINARY
XRT79L71
44
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
2.4
The need for TxInClk, in order to operate the Microprocessor Interface
In Revision A Silicon (which, at the time that this version of the Data Sheet was written, is the only revision of
the XRT79L71 that exists), the user is required to supply a clock signal at the TxInClk in order to permit the
Microprocessor Interface to function (e.g., support to READ and WRITE operations). The Microprocessor
Interface (internally) uses the TxInClk signal to update the registers within the XRT79L71. If a clock signal is
not applied to the TxInClk input pin, the Microprocessor Interface will NOT support READ or WRITE operations
AT ALL.
If the user is having problems performing READ and WRITE operations with the XRT79L71, check and verify
that a clock signal is present at the TxInClk input pin.
NOTES:
1.
The Microprocessor Interface needs for a clock signal to be present at the TxInClk input pin, even if the part has
been configured to operate in the Loop-Timing Mode (and if the System-Side Terminal Equipment is using the
RxOutClk as timing source for the 44.736MHz or 33.368MHz clock signal).
2.
This requirement will NOT be true for Revision B (and beyond) silicon. In the case of future silicon, the user will
need to make sure that the Receive DS3/E3 LIU Block is provided with either a Recovered Clock signal (from the
incoming line signal) or a Reference Clock Signal (which is derived from either a 12.288MHz, 34.368MHz or a
44.736MHz clock signal, via the SFM Synthesizer Block). Please see Section 3.3.1.5 for more details on the SFM
Synthesizer Block.
2.5
Reading out the DS3/E3 Framer Block Performance Monitor Registers
The DS3/E3 Framer Block PMON (Performance Monitor) Registers (below) are 16-bit "RESET-upon-READ"
registers. However, the manner in which these particular PMON Registers are to be read is listed below.
As mentioned earlier, these PMON Registers are 16-bits in length. More specifically each of these PMON
Registers will consist of a "MSB" (Most Significant Byte) 8-bit register, and a "LSB" (Least Significant Byte)
register. Since the Microprocessor Interface of the XRT79L71 contains an eight-bit wide bi-directional data
bus, the user will have to execute two consecutive read operations in order to obtain the full 16-bit content of a
given PMON register. As the contents of these PMON Registers are being read out, the following restrictions
apply.
FIGURE 12. ILLUSTRATION ON RECOMMENDATION ON HOW TO INTERFACE THE MICROPROCESSOR INTERFACE OF
THE
XRT79L71 TO THE MPC860, WHEN CONFIGURED TO OPERATE IN THE POWERPC 403 MODE
U6
MPC860/8260
CS
RWB
WE
OE
TS
TA
INT
A16
A17
A18
A19
A20
A21
A22
A23
A24
A25
A26
A27
A28
A29
A30
A31
D56
D57
D58
D59
D60
D61
D62
D63
PCLK
1
U8A
7404
1
2
HW_RESET
U5
XRT79L71
D14
B16
C15
J13
A16
C14
D13
F16
F15
F14
F13
G16
G15
G14
G13
C16
D15
D16
E16
E15
E14
E13
D11
C12
B13
A14
D12
C13
B14
A15
H16
M14
B15
H13
J16
J15
J14
CS
RW_L
RD_L
DBEN
AS_L
RDY_L
INT
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
A14
D0
D1
D2
D3
D4
D5
D6
D7
PCLK
RESET
BLAST_L
DirectAddrSel
PTYPE0
PTYPE1
PTYPE2
R13
4.7K
3.3V