XRT83SL38/L38EVAL User Manual
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APPLICATION CIRCUITRY
CPLD
The XRT83SL38/L38EVAL uses a CPLD designed to emulate a microprocessor support module
for an 8-Bit parallel interface. Using Exar’s GUI software (included in the evaluation kit), the
XRT83SL38/L38EVAL can be controlled through a standard parallel port cable connected to a
PC. The GUI was written to simplify the evaluation process of Exar’s LIU. Access to all the
control registers and functionality fo all four channels is available. For information on the GUI
software, see the “XRT83SL38/L38EVAL GUI SOFTWARE” section of this manual. Figure 2 is a
simplified block diagram of the CPLD interface.
CPLD
XRT83SL38
XRT83L38
LIU
25 DIN Connector
5
Parallel Port Cable
A[7:0]
D[7:0]
INT
PCLK
ALE
RST
HW/HOSTB
CS
WR
RD
RDY
PC
Figure 2 Simplified Block Diagram of the CPLD Interface
Line Interface Module
Internal Impedance Mode
The XRT83SL38/L38 has an internal and external impedance mode. For internal impedance
mode, no termination resistors are necessary for the transmit outputs. This allows the user to
have one bill of materials for all three applications. Figure 3 is a simplified block diagram of the
internal impedance mode. For external impedance mode, see the following sections for the
resistor values chosen for the corresponding application.
Line Interface Module
TTIP
TRING
RTIP
RRING
XRT83SL38/L38 LIU
0.47uF
Figure 3 Simplified Block Diagram of the Internal Impedance Mode
