Interface Bridging

Control planes feature a large number of ASSPs and microcontrollers, requiring an inexpensive and easy solution for translating between these interfaces. The MAX® series devices are designed to support interface bridging applications, including voltage-level shifting (for example, 3.3-volt input to 1.8-volt output), bus translation applications (translating a proprietary protocol to an industry-standard protocol), multipoint bus bridging, serial-to-parallel and parallel-to-serial bus conversions, and encryption.

Table 1. MAX II CPLD Application Solutions: Interface Bridging

MAX II CPLD Features

Customer Benefits

Low Cost per I/O

Bus-width requirements make higher I/O counts a necessity. Choose from a wide range of low cost MAX II CPLD package options and I/O counts.

PCI Compliance

Supports a direct interface to legacy PCI bus system (3.3-V, 66MHz), one of the most common protocols in the industry, with no additional external hardware.

Flexible I/O Banks

Multiple I/O banks support multiple I/O voltages, reducing the number of CPLDs per board.

Second-Time Fitting

Freeze your PCB pin-out earlier knowing that Altera's design software can handle logic changes, using it's flexible interconnect routing resources, even with locked pin assignments.


PLDs offer the flexibility to make changes throughout the design cycle (prototype, production, or field upgrades), allowing OEMs to add new features at anytime.

Figure 1 shows an example MAX II CPLD implementing a PCI bridge. In this application, MAX II CPLDs enable the addition of an optional add-on board to the host PCI bus system. The two largest MAX II CPLDs are PCI-compliant and may be added to a 3.3-V PCI bus as a 32-bit PCI target at 66 MHz. The boards may be physically separated via a cable or as part of a backplane configuration.

MAX II CPLDs can also act as repeaters for other bus systems, increasing the drive strength of the bus, and subsequently, the number of devices that can be supported on the bridge.

Figure 1. PCI Bus Bridge Using MAX II CPLDs

MAX II CPLDs can function as a crosspoint switch or multi-point connection. In this application, the logic in the MAX II CPLD is divided into three major blocks:

  1. Switch matrix - Connects any input to any output
  2. Configuration register - Reconfiguring connections during operation
  3. Address decoder - Decodes the output addresses of the configuration

Interface bridging requires a large number of I/O pins to support the bus interfacing, but not a lot of logic. Because MAX II CPLDs have a low cost per I/O and minimal logic, they are ideal for this type of application.

Related Links

  • Link to Design Store
  • etc.