Increasing the performance of GPIB-controlled VXI systems

The HS488 protocol increases the maximum GPIB transfer rate up to 8 Mbytes/s. By using a hardware signaling mechanism to enable HS488 and to handle the data transfer issues, this protocol meets the requirements of speed, compatibility, and transparency with existing systems. When choosing between GPIB and MXI for external control of a VXI system, one must take several factors into account. For message-based instruments, both MXI and GPIB transfer short strings at the same rate, because the VXI Word Serial Protocol is slower than GPIB. In the past, if one used message-based instruments, MXI was the only choice because GPIB was too slow. Now, with HS488, GPIB is comparable to MXI. So, the choice between the two communication protocols becomes a cost and configuration issue. If, however, one uses register-based instruments, GPIB is not the right choice. Instead, one should use an embedded controller or MXI. Regardless, because of its substantial performance increase, HS488 extends the usability of GPIB systems into the next generation of instrumentation