10.3.1 SPI Data Transfer Modes

SPI Arbitrary Data Transfer Modes

These modes allow the transfer of arbitrary data, under program control, via the SPI Modules.

Direct Transfer using SpiAPI methods.

To transmit data unidirectionally to an SPI Slave Device, use SpiAPITransmit.
To transmit a request to, and then receive a response from, an SPI Slave Device, use SpiAPITransceive.

In both cases, SpiModuleOutputSource must be set to DataSourceSpi.
Note in particular that DataSourceSpi is strictly necessary, and the only option, for bi-directional communication via SPI under program control.

Programming examples for this mode are shown in 10.3.2 SPI Programming using the SpiAPI.

Indirect Transfer via List Command.

To transmit data contained in a list command, call CommandListAppendSpiWrite to add the PERIPHERAL_SPI command, along with a suitable data-payload, to a CommandList.
The data will be transmitted to the SPI Slave Device when the PERIPHERAL_SPI command is executed.

In this case, SpiModuleOutputSource must be set to DataSourceSpiListCommand.

Programming examples for this mode are shown in 10.3.3 SPI Programming via CommandLists.

SPI Scanhead Return Channel Data Mode

Return Channel Data mode (RCD Mode) is used to output a scanhead's Return Channel Data stream via an SPI Module, thus allowing an SPI Slave Device to monitor the return channel data.

RCD Mode is enabled by setting SpiModuleOutputSource to DataSourceScannerCommunication.

A programming example for this mode is shown in 10.3.4 SPI Programming for Scanner Data Monitoring.

The SPI module transmits three 32-bit DWORDs containing the scanhead return channels X, Y, and Z, and some additional channel status information.
The return channel data from Scanhead 0 are output by both SPI modules 0 and 2, simultaneously.
The return channel data from Scanhead 1 are output by both SPI modules 1 and 3, simultaneously.

An SPI transfer will normally be started as soon as a complete return channel data frame is received from the scanhead by the SP-ICE-3

Please note, however, the following important exceptions to this general rule:

Scanner Protocol

SPI Frame Transfer

XY2-100

An SPI frame transfer happens strictly every 10μs because the return channel's clock signal is generated by the SP-ICE-3.

The three channels (X-, Y-, Z-axis channel) are always synchronised.

Note
If no scanner is connected, SPI frames will still be output, but only by modules 0 and 2 (but not on 1 and 3).

SL2-100/RL3-100

An SPI frame transfer happens only after an SL2-100/RL3-100 frame has been received.

Note
If no frames are received via the SL2/RL3 interface, e.g. when there is no scanhead connected, or the scanhead is connected but switched off, then no SPI data frames will be transmitted.

The SL2-100 protocol has no third channel for the Z-Axis, so the third channel is taken instead from the X-channel of the second SL2 interface.

Because the second SL2 interface has separate sync timing, it can happen that the Z-channel data is not updated synchronously with the X- and Y-channels from the first interface, thus allowing the Z-axis to appear to be (still) active after it has, in fact, been shut down.

Default SPI Signal Timing for RCD Mode

The clock rate is 16MHz and one transfer contains three 32-bit DWORDs.

The SYN pin is asserted LOW before the start of the transfer and deasserted HIGH after the last DWORD has been transfered.

The TXD pin is HIGH when inactive, but the data itself is not inverted (i.e. data bits are active HIGH).

The TXD changes on a falling edge of the CLK and shall be captured on a rising edge of the CLK.

Bit Positions for RCD Mode

Bit 31	Bit 30	Bit 29	Bit 28	Bit 27	Bit 26	Bit 25	Bit 24
RX_FRM20	RX_FRM18	RX_FRM16	RX_CMD	RX_PDO	RX_CHST	RX_USER	RX_VALID

Bit 23	Bit 22	Bit 21	Bit 20	Bit 19	Bit 18	Bit 17	Bit 16
RX_AUX3	RX_AUX2	RX_AUX1	RX_AUX0	RX_DAT19	RX_DAT18	RX_DAT17	RX_DAT16

Bit 15	Bit 14	Bit 13	Bit 12	Bit 11	Bit 10	Bit 9	Bit 8
RX_DAT15	RX_DAT14	RX_DAT13	RX_DAT12	RX_DAT11	RX_DAT10	RX_DAT9	RX_DAT8

Bit 15	Bit 14	Bit 13	Bit 12	Bit 11	Bit 10	Bit 9	Bit 8
RX_DAT7	RX_DAT6	RX_DAT5	RX_DAT4	RX_DAT3	RX_DAT2	RX_DAT1	RX_DAT0

Bit Descriptions for RCD Mode

Bit	Symbol	Description
31	RX_FRM20	Indicates whether the last received frame in the RX_DAT field has a valid 20 bit payload. This happens when SL2-100 is configured.
30	RX_FRM18	Indicates whether the last received frame in the RX_DAT field has a valid 18 bit payload. This happens when XY2-100 is configured and the scanhead sends either PDO or 18 bit data.
29	RX_FRM16	Indicates whether the last received frame in the RX_DAT field has a valid 16 bit payload. This happens when XY2-100 is configured and the scanhead sends 16 bit data.
28	RX_CMD	Indicates whether the last received frame in the RX_DAT field has a valid answer to a standard XY2-100 Enhanced or SL2-100 Enhanced command. In SL2-100 mode this is indicated by a set VALID bit. In XY2-100 mode this is indicated by a 16 bit frame type. So in XY2-100 mode Enhanced commands which result in a 18 bit frame will not set this bit.
27	RX_PDO	Indicates whether the last received frame in the RX_DAT is a Process Data Objekt (PDO). In SL2-100 mode a PDO is indicated by a cleared valid-bit and the number in the AUX-bits is not zero and indicates the PDO Number. In XY2-100 mode this bit is set when a 18 bit frame was received. The to LSBs indicate the PDO Number. The PDO Number is reflected in the AUX bits as in SL2-100.
26	RX_CHST	Contains the CHST bit in SL2-100 mode. Zero in XY2-100 mode.
25	RX_USER	Contains the USER bit in SL2-100 mode. Zero in XY2-100 mode.
24	RX_VALID	Contains the VALID bit in SL2-100 mode. Indicates a valid 18- oder 16 bit frame in XY2-100 mode. If this bit is set, the received return channel may contain the answer to a XY2-100 Enhanced command. In XY2-100 mode the received frame can bei either a 16 bit frame (which is always a valid answer to a command) or a 18 bit frame which can bei either a PDO or a answer to a Ehnahced command with 18 bit payload. In SL2-100 mode this bit equals the RX_CMD bit.
23:20	RX_AUX	Contains the AUX bits in SL2-100 mode. In XY2-100 mode there are no AUX bits but these bits are set in a way that reflects the AUX bits used to distinguish between PDOs in 18 bit mode and set to "1110" in 16 bit mode to indicate no scanhead error. When a command answer is received in SL2-100 mode (RX_CMD=1) these bits reflect the scanhed status bits: PowerOK, TempOK, PosAck, ASC. When a PDO is received the AUX bits indicate the PDO number: PDO1 = "0010 PDO2 = "0100" ... PDO6 = "1100". There is no PDO0 or PDO7. PDO0 (AUX = "0000") indicates an invalid frame.
19:0	RX_DAT	Contains the payload data from either SL2-100 or XY2-100. The data is always left alignd. (The MSB is always in bit 19, depending on 20-, 18- or 16 bit frame the LSB are zero.)

SPI RCD Mode Examples

Here are some typical examples of SPI data frames output in RCD Mode.

Current Position

This example shows the received data frame when the CurrentPosition is returned from the scanhead via the RAYLASE.SPICE3.ScannerEnhancedProtocol.

The asserted CMD bit in the register indicates a valid response to the command, regardless of whether it is received by XY2-100 or SL2-100. XY2-100 and SL2-100 can be distinguished by the FRM16/18/20 bits.

The payload will be a the same position regardless of being transfered by SL2-100 or XY2-100. In XY2-100 mode the last 4 LSB bits in the payload will be zero because XY2-100 can only transfer 16 bit.

Status Word

This example shows the received data frame when the scanhead is commanded to return the StatusWord via the RAYLASE.SPICE3.ScannerEnhancedProtocol.

Backwards compatible Status Word

This example shows the received data frame when the scanhead is commanded to return the CompatibleStatusWord via the RAYLASE.SPICE3.ScannerEnhancedProtocol, or in any case when an SS-II scanhead is connected.

This mode is only possible with XY2-100 and should not be used except with SS-II scanheads.

The register marks such frames as FRM18 and not as a CMD. The VALID bit is set nonetheless.

Note that the Status Word is shifted to right by one in the payload and the payload MSB ist always '1'.

Error

This example shows the received data frame when a unknown frame or a frame with an error is received.

Be aware that it is also possible in SL2-100 mode that no frame is received at all. In that case there will be no frame transmitted on the SPI bus.