XRT84L38 View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT84L38' PDF : 453 Pages View PDF
XRT84L38
OCTAL T1/E1/J1 FRAMER
REV. 1.0.1
5. Further, the µC/µP should indicate that this cycle is a Read cycle by setting the WR_R/W (R/W*) input pin
"High".
6. Next the µC/µP should initiate the current bus cycle by toggling the RD_DS (Data Strobe) input pin "Low".
This step enables the bi-directional data bus output drivers, within the Framer. At this point, the bi-direc-
tional data bus output drivers will proceed to drive the contents of the Address register onto the bi-direc-
tional data bus, D[7:0].
7. After some settling time, the data on the bi-directional data bus will stabilize and can be read by the µC/µP.
The Framer will indicate that this data can be read by asserting the RDY_DTACK (DTACK) signal “Low”.
8. After the µC/µP detects the RDY_DTACK signal (from the Framer) it will terminate the Read Cycle by tog-
gling the RD_DS (Data Strobe) input pin "High".
Figure 6 presents a timing diagram which illustrates the behavior of the Microprocessor Interface signals
during a Motorola-type Programmed I/O Read Operation.
FIGURE 6. MOTOROLA µP INTERFACE SIGNALS DURING A PROGRAMMED I/O READ OPERATION
ALE_AS
A[6:0]
CS
D[7:0]
RD_DS
WR_R/W
RDY_DTACK
Address of target Register
Not Valid
Valid Data
1.3.2.2.2.2
Motorola Mode Write Cycle
Whenever a Motorola-type µC/µP wishes to write a byte or word of data into a register or buffer location, within
the Framer, it should do the following.
1. Assert the ALE_AS (Address Select) input pin by toggling it "Low". This step enables the Address Bus
input drivers (within the Framer chip).
2. Place the address of the target register or buffer location (within the Framer), on the Address Bus input
pins, A[6:0].
3. While the µC/µP is placing this address value onto the Address Bus, the Address-Decoding circuitry (within
the user's system) should assert the CS (Chip Select) input pins of the Framer by toggling it "Low". This
step enables further communication between the µC/µP and the Framer Microprocessor Interface block.
4. After allowing the data on the Address Bus pins to settle (by waiting the appropriate Address Setup time),
the µC/µP should toggle the ALE_AS input pin "High". This step causes the Framer to latch the contents of
the Address Bus into its own circuitry. At this point, the Address of the register or buffer location (within the
Framer), has now been selected.
5. Further, the µC/µP should indicate that this current bus cycle is a Write operation by toggling the WR_R/W
(R/W*) input pin "Low".
6. The µC/µP should then place the byte or word that it intends to write into the target register, on the bi-direc-
tional data bus, D[7:0].
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