3 Integrating Multiple Host Controllers on a Single TPLD

As OSFP host side systems need to accommodate an ever growing number of pluggable modules, one of the major benefits of using TPLD for host controllers is the ability to integrate multiple host controllers in a single TPLD, providing space and cost savings in addition to reducing the number of devices. TPLD can be configured to contain multiple host controllers and communicate in a variety of ways. For example, the TPLD2001 has three configuration options when acting as an OSFP host controller.

1. Dual-channel host controller that communicates only via GPIO
2. Three-channel, fixed-address host controller that communicates via I²C
3. Dual-channel, GPIO-addressable host controller that communicates via I²C

The host configuration described in Section 2 relies on GPIO inputs to signal low power control and reset control. Up to two of these GPIO-input host controllers can fit into TPLD2001.

Interfacing with a host controller via I²C is another option. Many TPLDs have the ability to act as an I²C peripheral with a user-defined address. TPLD2001 can fit up to three OSFP host controllers in a single device, freeing up a lot of space and GPIO pins in the system. TPLD's I²C address is defined by the user but cannot be changed after the TPLD is permanently configured. If the designer is ordering pre-configured devices from TI, a single pre-configured orderable part number can only have one I²C address. Designs requiring more than three OSFP host controllers can use an I²C multiplexer or, more efficiently, TPLD's GPIO-addressable I²C.

Although TPLD can be ordered pre-configured with no additional charge, the devices can can also be configured by the user. All TPLDs that have I²C interfaces also allow the user to program the TPLDs on their own factory line by ordering unconfigured blank devices from TI. In this case, every TPLD can easily be configured with different addresses with only one orderable part number. More information about ordering pre-configured TPLD can be found in the Application Brief TPLD Ordering Process and information about in-system programming TPLD can be found in the Applicaiton Note Programming in Production with TPLD.

To provide each TPLD with a different I²C address, up to four bits of the I²C address are GPIO-selectable. The other three bits are defined by the user within the internal configuration. As a result, each TPLD orderable part number can have up to sixteen unique addresses. If more than sixteen unique addresses are required, adding additional TPLD configurations with a different address can allow up to a total of up to 126 unique addresses with eight orderable part numbers. Using GPIOs as address bits allows the designer to operate all the TPLD devices on the same I²C bus.