Byte Deserializer
The FPGA fabric-transceiver interface frequency has an upper limit. In configurations that have a receiver
PCS frequency greater than the upper limit stated, the parallel received data and status signals cannot be
forwarded directly to the FPGA fabric because it violates this upper limit for the FPGA fabric-transceiver
interface frequency. In such configurations, the byte deserializer is required to reduce the FPGA
fabric-transceiver interface frequency to half while doubling the parallel data width.
The byte deserializer is required in configurations that exceed the FPGA fabric-transceiver interface
clock upper frequency limit. It is optional in configurations that do not exceed the FPGA fabric-
transceiver interface clock upper frequency limit.
Note:
The byte deserializer supports operation in single- and double-width modes. The datapath clock rate at the
input of the byte deserializer is twice the FPGA fabric–receiver interface clock frequency. After byte
deserialization, the word alignment pattern may be ordered in the MSByte or LSByte position.
The data is assumed to be received as LSByte first—the least significant 8 or 10 bits in single-width mode or
the least significant 16 or 20 bits in double-width mode.
Table 1-27: Byte Deserializer Input Datapath Width Conversion
Receiver Output Datapath Width
Byte Deserializer Input
Datapath Width
Mode
16
8
Single Width
20
10
32
16
Double Width
40
20
Byte Deserializer in Single-Width Mode
In single-width mode, the byte deserializer receives 8-bit wide data from the 8B/10B decoder or 10-bit wide
data from the word aligner (if the 8B/10B decoder is disabled) and deserializes it into 16- or 20-bit wide data
at half the speed.
Figure 1-30: Byte Deserializer in Single-Width Mode
Byte
Deserializer
Receiver PCS Clock
/2
D1
D2
D3
D4
D2
D4
datain[7:0]
or
datain[9:0]
dataout[15:0}
or
dataout[19:0]
D1
D3
Byte Deserializer in Double-Width Mode
In double-width mode, the byte deserializer receives 16-bit wide data from the 8B/10B decoder or 20-bit
wide data from the word aligner (if the 8B/10B decoder is disabled) and deserializes it into 32- or 40-bit wide
data at half the speed.
Altera Corporation
Transceiver Architecture in Cyclone V Devices
1-45
Byte Deserializer
CV-53001
2013.05.06