Replicate ROM

Syntax

#pragma HLS memory replicate_rom variable(<rom_var_name>) max_replicas(<int>)

Description

This pragma can be used to replicate constant memory (i.e., arrays) to achieve better throughput (shorter cycle latency) at the expense of extra resource (e.g., block RAM). Typically when an array is implemented in block RAMs, there are up-to-two RAM ports to allow a maximum of two reads per clock cycle. To allow more parallel read accesses in each clock cycle, constant read-only memories (ROM) can be replicated by using this pragma.

The optional max_replicas can be used to control the maximum number of replicas. If a max_replicas of N is specified, SmartHLS will make sure to use no more than N replicas of the ROM in the generated circuit; the generated circuit may use less than N replicas when the throughput cannot be further improved with more replicas. When max_replicas is unspecified or set to 0, the number of replicas is unlimited and SmartHLS will use as many replicas as it needs to maximize throughput. A max_replicas of 1 means only one copy is allowed, hence no replication, equivalent to not having the pragma.

Parameters

Parameter	Value	Optional	Default	Description
max_replicas	<int>	Yes	0	The maximum number of replicas allowed

Position

Before the global / local variable declaration.

Examples

#pragma HLS memory replicate_rom variable(my_rom) max_replicas(10)
const int my_rom[100];