The SS1 to USB converters from PCA - Plant Control and Automation are designed to transmit data synchronously to the clock signal of the master device starting with the most significant bit (MSB).
When non-operational, clock and data line levels are high. As soon as the clock signal of a sequence changes for the first time from high(H) to low (L), data is latched for transmission. Data bits are shifted on rising clock edges starting with the most significant bit (MSB).Transmission ends on the last rising clock edge and is terminated after expiration of the SSI delay time (latch is cleared after at least 20 μs).The maximum data word length with SSI2USB is32 bits.
These USB converters are capable of gray to binary code conversion during process of sampling. For this purpose, the data word may be masked by a 32 bit word (AND mask) to cut status bits that are not object of conversion. Additionally, the overall data may be masked by another 32 bit word (AND mask) to cut out data that is of no interest. Especially the sample time (time interval between two consecutive transmissions of a single data batch) can be selected to be shorter than the actual SSI pause time for development purposes. This setting may cause the device under test to send the same data over and over again, since the latch may not be released between succeeding transmissions.
Some of the main features of these USB Converters include:
- SSI master device for USB connection
- Alternatively SPI master device via TTL level
- Three independent tri-state push-pull outputs
- Compact and robust aluminium housing
- Built in gray code to binary code conversion
- Power supply of SSI device from USB port (12 Volts up to 90 mA or 5 V up to 270 mA)
- External power supply can be connected
- Graphical user interface provided with device