The OpenCL programming advance guide explains about the RTL element required for the library for external memory.
For the AVALON_MEM element defined in the code example, the corresponding RTL module ports are as follows:
input [511:0] avm_port0_readdata,
output [31:0] avm_port0_address,
output [511:0] avm_port0_writedata,
output [63:0] avm_port0_byteenable,
output [4:0] avm_port0_burstcount,
There is no assumed correspondence between pointers that you specify with
MEM_INPUT and the Avalon-MM interfaces that you specify with AVALON_MEM. An RTL module can use a single pointer to address zero to multiple Avalon-MM interfaces
Both signals in bold are not documented.
In most applications the avm_port0_enable signal can be tied high, and the avm_port0_writeack signal can be ignored. An updated description will be included in the upcoming programming guide.