Intel® Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 10/04/2021
Public

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6.3. Tri-State Components

The tri-state interface type allows you to design Platform Designer subsystems that connect to tri-state devices on your PCB. You can use tri-state components to implement pin sharing, convert between unidirectional and bidirectional signals, and create tri-state controllers for devices whose interfaces can be described using the tri-state signal types.

Tri-State Conduit System to Control Off-Chip SRAM and Flash Devices

In this example, there are two generic Tri-State Conduit Controllers. The first is customized to control a flash memory. The second is customized to control an off-chip SSRAM. The Tri-State Conduit Pin Sharer multiplexes between these two controllers, and the Tri-State Conduit Bridge converts between an on-chip encoding of tri-state signals and true bidirectional signals. By default, the Tri-State Conduit Pin Sharer and Tri-State Conduit Bridge present byte addresses. Typically, each address location contains more than one byte of data.

Figure 224. Tri-State Conduit System to Control Off-Chip SRAM and Flash Devices

Address Connections from Platform Designer System to PCB

The flash device operates on 16‑bit words and must ignore the least‑significant bit of the Avalon memory mapped address. The figure shows addr[0]as not connected. The SSRAM memory operates on 32-bit words and must ignore the two low-order memory bits. Because neither device requires a byte address, addr[0] is not routed on the PCB.

The flash device responds to address range 0 MB to 8 MB-1. The SSRAM responds to address range 8 MB to 10 MB-1. The PCB schematic for the PCB connects addr[21:0] to addr[18:0] of the SSRAM device because the SSRAM responds to 32‑bit word address. The 8 MB flash device accesses 16‑bit words; consequently, the schematic does not connect addr[0]. The chipselect signals select between the two devices.

Figure 225. Address Connections from Platform Designer System to PCB
Note: If you create a custom tri-state conduit host with word aligned addresses, the Tri‑state Conduit Pin Sharer does not change or align the address signals.
Figure 226. Tri-State Conduit System in Platform Designer