HC4GX15 Datasheet, PDF (303/668 Pages) Altera Corporation – HardCopy IV Device Handbook

Chapter 1: HardCopy IV GX Transceiver Architecture
1–39
Transmitter Channel Datapath
For example, if you want to run the transceiver channel at 6.25 Gbps, without the byte
serializer, in double-width mode, the core fabric interface clock frequency must be
312.5 MHz (6.25/20). This violates the core fabric interface frequency limit. When you
use the byte serializer, the core fabric interface frequency is 156.25 MHz (6.25G/40).
You can enable the byte serializer in single-width or double-width mode.
1 The byte deserializer is required in configurations that exceed the core
fabric-transceiver interface maximum frequency limit. It is optional in configurations
that do not exceed the core fabric-transceiver interface maximum frequency limit.
f For more information about the maximum frequency limit for the transceiver
interface, refer to the HardCopy IV Device Datasheet in volume 4 of the HardCopy IV
Device Handbook.
Single-Width Mode
Figure 1–23 shows the byte serializer datapath in single-width mode.
Figure 1–23. Byte Serializer Datapath in Single-Width Mode (Note 1), (2)
datain[]
Byte Serializer ^dataout[]
/2
Low-Speed Parallel
Clock
Notes to Figure 1–23:
(1) Refer to Table 1–6 on page 1–39 for the datain[] and dataout[] port widths.
(2) The datain signal is the input from the core fabric that has already passed through the TX phase compensation
FIFO.
The byte serializer forwards the least significant byte first, followed by the most
significant byte. The input data width to the byte serializer depends on the channel
width option that you selected in the ALTGX MegaWizard Plug-In Manager. For
example, in single-width mode, assuming a channel width of 20, the byte serializer
sends out the least significant word datain[9:0] of the parallel data from the core
fabric, followed by datain[19:10]. Table 1–6 shows the input and output data
widths of the byte serializer in single-width mode.
Table 1–6. Input and Output Data Width of the Byte Serializer in Single-Width Mode
Deserialization Width
Single-width mode
Input Data Width to the Byte
Serializer
16
20
Output Data Width from the
Byte Serializer
8
10
© June 2009 Altera Corporation
HardCopy IV Device Handbook Volume 3