Tiles — Project Trellis documentation

# Tiles

The ECP5 FPGA is structured as a grid of tiles. This grid can be visualised by looking at the HTML output of `tile_html.py`.

Tiles have a name, for example MIB_R13C6 and a type, for example MIB_DSP2. The name also encodes a position, in this case row 13, column 6. Multiple tiles may be located in the same grid square.

Tiles also have an offset in the bitstream in terms of frames and bits within frames, and a bitstream size in terms of frames and bits within frames.

## Logic Tiles

All logic tiles are of type PLC2.

Logic Tiles contain 4 slices and routing fabric. The routing fabric in a logic tile can connect slices to general and global routing; and connect together general routing wires.

Each slice contains 2 LUTs, 2 flip-flops and fast carry logic. All slices can also be configured to function as distributed RAM.

## Common Interconnect Blocks (CIBs)

Common Interconnect Blocks (CIBs) are used to connect special functions - everything other than slices - to the routing fabric. They are effectively a logic tile with the slices removed, and the signals that would connect to the slice are connected to inputs and outputs from those special functions. Special functions in this context includes IO, EBR, DSPs, PLLs, etc. Note that the names of these signals do not reflect the IO of the special function, but are always named as if they were connected to a slice. Part of Project Trellis will thus be determining this mapping.

There are several types of CIB depending on what they connect to and their location on the chip. For example:

> - CIB tiles connect to top and bottom IO, and CIB_LR connect to left and right IO.

> - CIB_EBR tiles connect to EBR.

> - CIB_DSP tiles connect to the hard DSPs.

> - CIB_PLLx tiles connect to the PLLs.

> - CIB_DCUx tiles connect to the SERDES duals (DCUs).

Most CIBs contain a CIBTEST component, which has an unknown function in Lattice testing but is not used for user designs.

## IO Tiles

There are several different types of IO tiles depending on the position in the device. In all cases, each IO pin is represented by two sites: an IO buffer (`PIO`) and IO registers/gearboxes (`IOLOGIC`).

Depending on the location in the device, IO pins are arranged in quads (A-D) or pairs (A-B).

> - IO at the top of the device uses a total of four tiles for each pair of IO. PIOT0 and PIOT1 contain `PIOA` and `PIOB` split between them, and PICT0 and PICT1 contain `IOLOGICA` and `IOLOGICB`.

> - IO at the left and right of the device use a total of three tiles for each quad of IO. Note that in this context x is L for left IO and R for right IO. PICx1 contains all four PIO, PICx0 contains `IOLOGICA` and `IOLOGICB`, and PICx2 usually contains `IOLOGICC` and `IOLOGICD`. In some cases, `IOLOGICC` and `IOLOGICD` are placed inside a MIB_CIB_LR tile instead.

> - IO at the bottom of the device uses a total of two tiles for each pair of IO. PICB0 and PICB1 contain both PIO and IOLOGIC split between them.

Additionally BANKREFx tiles contain per-bank IO configuration for reference voltages and VccIO.

## Global Clock Tiles

Several different tiles have functions in global clock routing. See Global Routing for more information on exact connections and blocks involved.

> - TAP_DRIVE and TAP_DRIVE_CIB tiles, arranged in several columns and present in all rows, selectively connect vertical global clocks coming in from the spine for the relevant quadrant to horizontal clock routing for the associated row section.

> - CMUX_xx tiles form the central global clock muxes for each quadrant, selecting clocks from the xMID tiles, feeding the spine tiles. In some cases these are split and/or combined with another function (such as DSP or EBR). These also contain the two clock selectors (DCSs).

> - xMID_x tiles select various input clocks and feed them to the central clock mux, providing a clock gate (DCC) for each clock.

> - ECLK_L and ECLK_R select the IO edge clocks.

> - x_SPINE_xx tiles selectively connect the outputs from the central clock muxes to the vertical wires feeding the TAP_DRIVE s. These are combined with another function, EBR or DSP and located in EBR/DSP rows.

## Embedded Block RAM (EBR)

The EBR is distributed such that 9 columns contain 4 EBRs (each EBR is 18kbit). The tiles containing the EBR sites themselves, and the EBR configuration bits, are named MIB_EBR0 to MIB_EBR8. The EBR is connected to the routing fabric using CIB_EBR tiles in the same row as the MIB_EBRx tiles. The meaning of MIB is unknown, it likely comes from Maco Interface Tile (Maco was a hybrid FPGA/ASIC technology previously used by Lattice).

The EBR configuration is split thus:

EBR | Tiles
--- | ---
0 | MIB_EBR0, MIB_EBR1
1 | MIB_EBR2, MIB_EBR3, MIB_EBR4
2 | MIB_EBR4, MIB_EBR5, MIB_EBR6
3 | MIB_EBR6, MIB_EBR7, MIB_EBR8

EBR initialisation is done using separate commands in the bitstream, not from within the EBR tiles themselves.

## DSP Tiles

DSPs are distributed such that 9 columns contain 2 18x18 sysDSP slices. Two tiles per column (on the same row) contain the DSP sites themselves, and the DSP configuration bits, and are named MIB_DSP0 to MIB_DSP8 and MIB2_DSP0 to MIB2_DSP8. The DSPs are connected to the routing fabric using CIB_DSP tiles in the same row as the MIBx_DSPx tiles.

## System and Config Tiles

There are several tiles, usually only one of each per device, which contain miscellaneous system functions and global device settings. For example:

> - EFBx_PICBx tiles (which are combined with bottom IO tiles) contain config port related settings such as which ports are enabled after configuration, whether TransFR is enabled, and the speed of the internal oscillator. They also contain configuration related to the global set/reset signal.

> - DTR contains the Digital Temperature Readout function.

> - POR contains a single bit to disable power-on reset.

> - OSC contains the internal oscillator.

> - PVT_COUNTx are related to Process/Voltage/Temperature compensation and contain a PVTTEST component for Lattice testing.