XRT94L33IB-L Exar Corporation, XRT94L33IB-L Datasheet - Page 133

• Manufacturer Part Number: XRT94L33IB-L
• Description: IC MAPPER DS3/E3/STS-1 504TBGA
• Manufacturer: Exar Corporation

Specifications of XRT94L33IB-L

• Applications: Network Switches
• Interface: Bus
• Voltage - Supply: 3.14 V ~ 3.47 V
• Package / Case: 504-LBGA
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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XRT94L33
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
Rev.1.2.0.
1.3.4.2
T
M
M
W
C
HE
OTOROLA
ODE
RITE
YCLE
Whenever a Motorola-type µC/µP wishes to write a byte or word of data into a register or buffer location,
within the UNI, 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 UNI chip).
2. Place the address of the “target” register or buffer location (within the UNI), on the Address Bus input pins,
A[14:0].
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 UNI by toggling it “low”. This
step enables further communication between the µC/µP and the UNI 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 UNI device 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 UNI), has now been selected.
5. Further, the µC/µP should indicate that this current bus cycle is a “Write” operation by toggling the
WRB_RW (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-
directional data bus, D[15:0].
7. Next, the µC/µP should initiate the bus cycle by toggling the RdB_DS (Data Strobe) input pin “low”. When
the XRT94L33 senses that the WRB_RW (R/W*) input pin is “high” and that the RdB_DS (Data Strobe) input
pin has toggled “low”, it will enable the “input drivers” of the bidirectional data bus, D[7:0].
8. After waiting the appropriate time, for this newly placed data to settle on the bi-directional data bus (e.g.,
the “Data Setup” time) the UNI will assert the Rdy_Dtck output signal.
9. After the µC/µP detects the Rdy_Dtck signal (from the UNI), the µC/µP should toggle the RdB_DS input
pin “high”. This action accomplishes two things.
a. It latches the contents of the bi-directional data bus into the XRT94L33 Microprocessor Interface block.
b. It terminates the “Write” cycle.
Figure 7 presents a timing diagram which illustrates the behavior of the Microprocessor Interface signals,
during a “Motorola-type” Programmed I/O Write Operation.
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