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PRELIMINARY
XRT79L71
40
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
Configuring the Microprocessor Interface to operate in the PowerPC 403 Mode
Configure the Microprocessor Interface to operate in the Intel-Asynchronous Mode by tying the PTYPE2 and
PTYPE0 pins/balls (e.g., Ball Numbers J14 and J16, respectively) to a logic "high", and by tying PTYPE 1 (Ball
Number J15) to GND.
Finally, if the Microprocessor Interface has been configured to operate in the Intel-Asynchronous Mode, then it
will perform READ and WRITE operations as described below.
2.3.1
The PowerPC 403 Read-Cycle
If the Microprocessor Interface (of the XRT79L71) has been configured to operate in the PowerPC 403 Mode,
then the Microprocessor should do all of the following, anytime it wishes to read out the contents of a register
or some location within the Receive LAPD Message buffer, the Receive Cell Extraction Memory or the
Transmit Cell Extraction Memory (within the XRT79L71).
1.
As the Microprocessor executes all of the following steps, it should designate this particular bus cycle as
a READ Operation by making sure that the WR/R/W (R/W) input pin is held at a logic "high".
2.
Place the address of the "target" register or buffer location (within the XRT79L71) on the Address Bus
input pin, A[14:0].
NOTE:
As the Microprocessor places this address value, on the Address Bus, the user should make sure that the
Microprocessor respects the "Address to Rising edge of
PCLK Set-up time" requirements.
WR/R/W
B16
I
Read/Write Operation Identification Input - R/W
If the Microprocessor Interface is configured to operate in the Power PC
403 Mode, then this input pin will function as the "Read/Write Operation
Identification Input" pin.
Anytime the Microprocessor Interface samples this input signal at a logic
low (while also sampling the
CS input pin "low") upon the rising edge of
PCLK, then the Microprocessor Interface will (upon the very same rising
edge of
PCLK) latch the contents of the Address Bus (A[14:0]) into the
Microprocessor Interface circuitry, in preparation for this forthcoming
READ operation. At some point (later in this READ operation) the Micro-
processor will also assert the DBEN/OE input pin, and the Microproces-
sor Interface will then place the contents of the "target" register (or
address location within the XRT79L71) upon the Bi-Directional Data Bus
pins (D[7:0]), where it can be read by the Microprocessor.
Anytime the Microprocessor Interface samples this input signal at a logic
high (while also sampling the
CS input pin a logic "low") upon the rising
edge of
PCLK, then the Microprocessor Interface will (upon the very
same rising edge of
PCLK) latch the contents of the Address Bus
(A[14:0]) into the Microprocessor Interface circuitry, in preparation for the
forthcoming WRITE operation. At some point (later in this WRITE opera-
tion) the Microprocessor will also assert the RD/DS/WE input pin, and the
Microprocessor Interface will then latch the contents of the Bi-Directional
Data Bus (D[7:0]) into the contents of the "target" register or buffer loca-
tion (within the XRT79L71).
DBEN
J13
I
Data Bus Enable Input:
For PowerPC Mode operation, the user should tie this pin to the OE out-
put (from the MPC860/8260 Microprocessor, or similar pin).
This input pin will be sampled upon the rising edge of
PCLK.
BLAST
B15
I
NONE - Tie this pin to GND
TABLE 6: THE ROLES OF VARIOUS MICROPROCESSOR INTERFACE PINS, WHEN CONFIGURED TO OPERATE IN THE
POWERPC 403 MODE
PIN NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION