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7 Series FPGAs SelectIO Resources User Guide www.xilinx.com 153
UG471 (v1.5) May 15, 2015
Input Serial-to-Parallel Logic Resources (ISERDESE2)
MEMORY_DDR3 Interface Type
The MEMORY_DDR3 mode has a complex clocking structure as a result of the DDR3
memory requirements. This INTERFACE_TYPE attribute setting is only supported when
using the MIG tool.
ISERDESE2 Width Expansion
Two ISERDESE2 modules can be used to build a serial-to-parallel converter larger than 1:8.
In every I/O tile there are two ISERDESE2 modules; one master and one slave. By
connecting the SHIFTOUT ports of the master ISERDESE2 to the SHIFTIN ports of the
slave ISERDESE2 the serial-to-parallel converter can be expanded to up to 1:10 and 1:14
(DDR mode only).
Figure 3-8 illustrates a block diagram of a cascaded DDR serial-to-parallel converter using
the master and slave ISERDESE2 modules. In the case of a 1:10 SERDES, slave ports Q3–Q4
are used for the last two bits of the parallel interface.
For a differential input, the master ISERDESE2 must be on the positive (_P pin) side of the
differential input pair. When the input is not differential, the input buffer associated with
the slave ISERDESE2 is not available, and so cascading cannot be used.
Guidelines for Expanding the Serial-to-Parallel Converter Bit Width
1. Both ISERDESE2 modules must be adjacent master and slave pairs. Both ISERDESE2
modules must be in NETWORKING mode because width expansion is not available in
MEMORY mode.
2. Set the SERDES_MODE attribute for the master ISERDESE2 to MASTER and the slave
ISERDESE2 to SLAVE. See SERDES_MODE Attribute.
3. The user must connect the SHIFTIN ports of the SLAVE to the SHIFTOUT ports of the
MASTER.
X-Ref Target - Figure 3-8
Figure 3-8: Block Diagram of ISERDESE2 Width Expansion
UG471_c3_08_012211
ISERDESE2
Master
Q1
SHIFTOUT2
D
Data In
Q2
Q3
Q4
Q5
Q6
Q7
Q8
SHIFTOUT1
Bit 0
Data Internal [0:7]
Data Internal [8:13]
ISERDESE2
Slave
Q1
SHIFTIN2
D
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Bit 13
SHIFTIN1
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