USB Instruments TIMS-0102 SPI Details

TIMS-0102 SPI Functionality

The TIMS-0102 provides a dedicated DB-15S connector for SPI communications. The SPI clock rate is programmable.The TIMS-0102 comes with eight chip-select lines. These chip select lines can be optionally configured so that four lines are used as and addres , with a separate chip-select line. The TIMS-0102 operates as an SPI bus Master.

Drive Current

The TIMS-0102 can drive all output signals with a maximum of 25 mA current source or sink.

Transmit (Tx) Clocking

The Tx clock idle state is configurable to be high or low. Tx can also be configured to the falling or rising edge.

Receive (Rx) Clocking

The Rx clocking can be configured so that it is sampled at the middle or end of the Tx output period.

Clock Rates and Speed

The TIMS-0102 supports 766 clock rates between 1.44 KHz and 10 MHz. Three overlapping ranges, each with 255 supported clock rates, exist for SPI communications. The driver software simplifies configuration by allowing "Target" clock rates to be specified. The actual clock rates are calculated and returned by the driver.

Throughput

Overall command and data throughput to an SPI device from a host computer through the TIMS-0102 module can be affected by many variables, including command setup time and the USB bus overhead.

There is additional overhead of sending commands and data over the USB bus between the Host computer and the TIMS-0102 module that will affect overall throughput from your application program. Individual commands will be executed at the hardware timed clock rates but overall throughput will be limited due to USB communications overhead.

Chip Select

Several modes of operation exist for performing chip select functionality.

Mode 1 -  Eight independent chip-select lines, with support for 5V CMOS logic levels

Mode 2  - Master mode operation. A 4-bit address and an nEN (Not Enable) are available for connection to the user's chip-select decode circuitry.

Microwire Compatibility

The TIMS-0102 is compatible with the Microwire protocol (a subset of the SPI protocol), except that the TIMS-0102 uses dedicated Tx and Rx lines. The Tx line is a dedicated serial data output line and the Rx is a dedicated serial data output line.

Known Limitations

The TIMS-0102 firmware version 1.0 supports only Master mode operation. Multi-master and slave mode operation will be supported in a future version of the firmware and will be field upgradeable.

Devices connected to the TIMS-0102 SDI line must be tri-stated during I2C operation. SCK will be active during an I2C operation.