Measured Loading Speed of Maxim's Serial Interface Software - AN813

This application article presents the three-wire bus speed generated by Maxim software running on various personal computers. Processor speeds tested ranged from 233MHz to 933MHz. Windows 95 and Windows 98 operating systems were used. The parallel printer port of the PC is monitored with a logic analyzer to capture the serial bus transmissions. The 24-bit register of the MAX2361 is loaded in 204μs to 118.4μs, depending on the operating system and the processor clock frequency. Additional Information: ● Wireless Product Line Page ● Quick View Data Sheet for the MAX2360 ● Applications Technical Support Maxim provides software to program the internal registers of many products using the three-wire SPI (serial peripheral interface) bus. The software accomplishes the bus loading operation by "bit-banging"1 on the parallel printer port of a personal computer. One undocumented aspect of this software is the speed at which the data is transported over the serial bus. Many SPI ICs support clock rates of 10MHz or greater. This application note presents the serial interface performance on a variety of computers. The load time for a 24-bit long register, such as found in the MAX2361, ranged from 118μs to 204μs on average. The software used for this test is the "Maxim Interface Software Version 5.00.26". The Test Environment Four different IBM compatible PCs were used to evaluate the impact of different processor clock speeds, memory sizes, and operating systems. Table 1. Personal Computers Used to Test Software Dell 4100 Desktop IBM T20 Notebook HP Pavilion 6470Z Desktop Sony Vaio PV220 Desktop Operating System Win 98 Second Edition Win 98 Second Edition Win 98 Win 95 Processor (P = Pentium) P III PIII PII PII Processor Speed 933MHz 750MHz 400MHz 233MHz DRAM 128M 96M 96M 32M On each machine, only one parallel printer port is installed. To monitor the signals appearing on the printer port, a logic analyzer was connected as show in Figure 1. Figure 1. Interface between the logic analyzer and the personal computer.