# A Multi-Channel Data Simulator Based on the Time Unification System
###### Abstract
[9] utilized peripheral component  
Figure 1: The real working environment of the target system and the working environment under simulation conditions. interconnect express (PCIe), a Field-Programmable Gate Array (FPGA), and Double Data Rate Synchronous Dynamic Random Access Memory (DDR) to implement the buffering and transmission of simulated data, achieving closed-loop self-checking for data transmission and reception. However, due to the Direct Memory Access (DMA) transmission mechanism of PCIe, it lacks the capability for real-time high-speed data transmission and reception, thus failing to achieve real-time closed-loop simulation. To achieve closed-loop simulation and emulate the real operating conditions of the target system, [PERSON] et al. [10] and [PERSON] et al. [11] implemented a multi-channel simulator that facilitates the conversion of data transmission protocols. However, the real-time simulated data generation is carried out on the simulator board. Due to its limited computational power, the simulator can only perform simple simulated data generation. [PERSON] et al. [12] utilized Graphics Processing Unit (GPU) acceleration to generate simulator data, enabling the creation of complex simulated data. Nonetheless, due to the lack of input from the target system's processing results, this system can only produce simulated data based on fixed configurations. [PERSON] et al. [13] and [PERSON] et al. [14] proposed the SpaceWire and SpaceFibre test equipment based on the PXI industrial standard, which can be used to generate and store the data required by the payload equipment. However, their external trigger signals still require additional PXI peripheral modules for implementation, and their high-speed interfaces can only generate fixed test data packets, failing to produce simulated data based on real operating scenarios. The main contribution of this study is that during the simulation process of the target system, the proposed data simulator can generate simulated data that are consistent with the real environment through a unified time reference, reducing the data differences between the simulation and real working conditions. There are two innovative points highlighted in this study:  
1. The proposed data simulator can receive Pulse-Per-Second (PPS) signals generated by the time reference generator. Through time synchronization, the simulator can achieve unified time with the target system, realizing data simulation under the real working conditions of the system. 2. The simulator can generate multiple channels of simulated data synchronized with the PPS signal, supporting various high-speed and low-speed interface protocols. It can send preset simulated data or generate simulated data in real time through the host computer, thereby achieving the closed-loop simulation verification of the target system. This study introduces a multi-channel data simulator based on a time unification system. The complete simulation system includes the host computer, simulator, target system, and time reference generator. The simulator has two working modes: storage mode and real-time mode. The simulator has programmable input and output interfaces for multi-channel protocols, allowing for the simulation and storage of high-speed and low-speed data and control signals. In the storage mode, the simulated data on the host computer are transmitted to the simulator's storage before simulation. Each channel of the interface sends data streams and control signals to the target system according to the time reference generator, while the simulator simultaneously stores the results output by the target system. In the real-time mode, the host computer generates simulated data and outputs them through the simulator in real time based on the results of the target system. Through experimental verification, it was found that the data simulator proposed in this study can achieve 4.2 Gbps of simulated data transmission and 1.6 Gbps of data reception and storage, with a closed-loop delay of 39.9 us.