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XRT83SL28
REV. 1.0.0
8-CHANNEL E1 SHORT-HAUL LINE INTERFACE UNIT
4.0 SERIAL MICROPROCESSOR INTERFACE BLOCK
The serial microprocessor uses a standard 3-pin serial port with CS, SCLK, and SDI for programming the LIU.
Optional pins such as SDO, INT, and RESET allow the ability to read back contents of the registers, monitor
the LIU via an interrupt pin, and reset the LIU to its default configuration by pulling reset "Low" for more than
10µS. A simplified block diagram of the Serial Microprocessor is shown in Figure 26.
FIGURE 26. SIMPLIFIED BLOCK DIAGRAM OF THE SERIAL MICROPROCESSOR INTERFACE
SDO
INT
CS
SCLK
SDI
Serial
Microprocessor
Interface
HW/Host
RESET
4.1
Serial Timing Information
The serial port requires 16 bits of data applied to the SDI (Serial Data Input) pin. The Serial Microprocessor
samples SDI on the rising edge of SCLK (Serial Clock Input). The data is not latched into the device until all 16
bits of serial data have been sampled. A timing diagram of the Serial Microprocessor is shown in Figure 27.
FIGURE 27. TIMING DIAGRAM FOR THE SERIAL MICROPROCESSOR INTERFACE
CS
25nS
50nS
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
SCLK
SDI
1
R/W
A0
A1
A2
A3
A4
A5
X
D0
D0
D1
D2
D3
D4
D5
D6
D7
High-Z
High-Z
D1
D2
D3
D4
D5
D6
D7
SDO
31
EXAR [ EXAR CORPORATION ]
