SPRUHX5I August 2014 – May 2024 TMS320F28374S , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376S , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378S , TMS320F28379S
The PUSH and PULL operations of the HLC are intended for data exchange with the host system. There are separate FIFO buffers for PUSH and PULL operations. For example, a series of PUSH operations write to successive locations in a linearly mapped-memory buffer. The PUSH buffer and the PULL buffer are mapped at address offsets shown in the Registers section.
The CPU can read from and write to the PUSH and PULL buffers, respectively, to exchange data with the HLC. Data pushed by the HLC is read by the CPU from the PUSH buffers. Data sent from the CPU to the HLC is written by the CPU to the PULL buffer and is read by the HLC using the PULL instruction.
Refer to clb_ex13_push_pull for guidance on properly using the PUSH and PULL buffers. To make use of one of the CLB inputs as a GPREG, have this input indicate when data is written to the FIFO by the CPU.
There are separate PUSH and PULL address pointers that increment each time the HLC performs a PUSH or PULL operation. These address pointers are also memory-mapped so that the CPU can determine the value. These address pointers are also writable and can be reset by the CPU at any time.
Overflow and underflow detection is done by simply reading the values of the PUSH and PULL address pointers.
In the CLB module of the device, the depth of the PUSH and PULL FIFOs is four 32-bit words each. If the CPU starts a fresh data transfer to the PULL buffers and sees the address pointer greater than four, then an underflow has occurred since the HLC has pulled more data than the number of words written by the CPU into the buffer.