2.6.3 R-Cell

The R-cell, the sequential logic resource of the Axcelerator devices, is the second logic module type in the AX family architecture. It includes clock inputs for all eight global resources of the Axcelerator architecture as well as global presets and clears (see the following figure).

The main features of the R-cell include the following:

  • Direct connection to the adjacent logic module through the hardwired connection DCIN. DCIN is driven by the DCOUT of an adjacent C-cell via the Direct-Connect routing resource, providing a connection with less than 0.1 ns of routing delay.
  • The R-cell can be used as a standalone flip-flop. It can be driven by any C-cell or I/O modules through the regular routing structure (using DIN as a routable data input). This gives the option of using the R-Cell as a 2:1 MUXed flip-flop as well.
  • Provision of data enable-input (S0)
  • Independent active-low asynchronous clear (CLR)
  • Independent active-low asynchronous preset (PSET). If both CLR and PSET are low, CLR has higher priority
  • Clock can be driven by any of the following (CKP selects clock polarity).
    • One of the four high performance hardwired fast clocks (HCLKs)
    • One of the four routed clocks (CLKs)
    • User signals
  • Global Power-On Clear (GCLR) and Global Power-On Preset (GPSET), which drive each flip-flop on a chip-wide basis.
    • When the Global Set Fuse option in the Designer software is unchecked (by default), GCLR = 0 and GPSET = 1 at device power-up. When the option is checked, GCLR = 1 and GPSET = 0. Both pins are pulled High when the device is in user mode. For information on simulation support, see the “Simulation Support for GCLR/GPSET in Axcelerator” section in the Antifuse Macro Library Guide.
  • S0, S1, PSET, and CLR can be driven by routed clocks CLKE/F/G/H or user signals.
  • DIN and S1 can be driven by user signals.

As with the C-cell, the configuration of the R-cell to perform various functions is handled automatically for the user through Microchip's extensive macro library (for a complete listing of available AX macros, see the Antifuse Macro Library Guide).

Figure 2-32. R-Cell