XRT73L03 View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT73L03' PDF : 62 Pages View PDF
áç
PRELIMINARY
3 CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT XRT73L03
REV. P1.0.13
A5 must be set to "0" as shown in Figure 33.
Bit 8 - A6:
The value of "A6" is a don't care.
Once these first 8 bits have been written into the Mi-
croprocessor Serial Interface, the subsequent action
depends upon whether the current operation is a
Read or Write operation.
Read Operation
Once the last address bit (A4) has been clocked into
the SDI input, the Read operation proceeds through
an idle period lasting two SClk periods. On the falling
edge of SClk Cycle #8 (see Figure 33) the serial data
output signal (SDO) becomes active. At this point,
reading the data contents of the addressed Com-
mand Register at Address [A4, A3, A2, A1, A0] via
the SDO output pin can begin. The Microprocessor
Serial Interface outputs this five bit data word (D0
through D4) in ascending order with the LSB first, on
the falling edges of the SClk pin. Consequently, the
data on the SDO output pin is sufficiently stable for
reading by the Microprocessor on the very next rising
edge of the SClk pin.
Write Operation
Once the last address bit (A4) has been clocked into
the SDI input, the Write operation proceeds through
an idle period lasting two SClk periods. Prior to the
rising edge of SClk Cycle # 9 (see Figure 33). Apply
the desired eight bit data word to the SDI input pin via
the Microprocessor Serial Interface. The Micropro-
cessor Serial Interface latches the value on the SDI
input pin on the rising edge of SClk. Apply this word
(D0 through D7) serially, in ascending order with the
LSB first.
Simplified Interface Option
The design of the circuitry connecting to the Micro-
processor Serial Interface can be simplified by tying
both the SDO and SDI pins together and reading data
from and/or writing data to this combined signal. This
simplification is possible because only one of these
signals are active at any given time. The inactive sig-
nal is tri-stated.
NOTES:
1. A5 is always "0"
2. R/W = "1" for "Read" Operations
3. R/W = "0" for "Write" Operations
4. Shaded blocks denotes a "don't care" value
FIGURE 33. MICROPROCESSOR SERIAL INTERFACE DATA STRUCTURE
CS
SClk
SDI
SDO
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
R/W A0 A1 A2 A3 A4 0 A6 D0 D1 D2 D3 D4 D5 D6 D7
High Z
High Z
D0 D1 D2 D3 D4 0 0 0
56
Share Link: 
