VHDL: 8 x 64 Shift Register with Taps


This example describes an 8-bit wide, 64-bit long shift register with equally spaced taps in VHDL. Synthesis tools detect groups of shift registers and infer altshift_taps megafunction depending on the target device architecture.

Figure 1. 8x64 shift register top-level diagram.

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Table 1. 8x64 Shift Register Port Listing

Port Name Type Description
clk Input Clock
shift Input Shift enable input
sr_in[7..0] Input 8-bit shift register input
sr_tap_one[7:0] Output 8-bit output of first tap
sr_tap_two[7:0] Output 8-bit output of second tap
sr_tap_three[7:0] Output 8-bit output of third tap
sr_out[7:0] Output 8-bit shift register output