ADS7953-Q1: Auto-2 Mode Sequence

Eric Sklarchuk

Part Number: ADS7953-Q1

NOTE: I am using device ADS7953-Q1.
NOTE: I am using datasheet ADS79xx (SLAS605C) in my references below, because it appears there are multiple errors in datasheet ADS79xx-Q1 (SBAS652A), i.e. Figure 54.

I am implementing an FPGA to control the SPI port of the ADS7953-Q1.

The design needs to sample all 16 channels at a pre-defined system frame rate (i.e. 10ms). The sequence repeats every 10ms. I wish to reset and reconfigure the device each frame.

Can you please verify the sequence I have listed below is acceptable:

Register	Action (For Next Frame)	Mode	SDI SPI Command	Sample and Convert Channel; Frame	MUX Channel Selected	SDO; Frame	Frame
GPIO Program Register	Reset Device	Manual	0x4200	N/A	CH0 Manual	Don't Care	n-2
Auto-2 Program Register	Set Last Channel	Manual	0x93C0	CH0 Manual; n-2	CH0 Manual	Don't Care	n-1
Auto-2 Mode Register	Change to Auto-2 Mode; Reset to CH0	Auto-2	0x3C00	CH0 Manual; n-1	CH0 Manual	CH0 Manual; n-1	n
Auto-2 Mode Register	Auto-2 Mode; Increment Channel Mode	Auto-2	0x3800	CH0 Manual; n	CH0 Auto-2	CH0 Manual; n	n+1
Mode Control Register	Continued Operation	Auto-2	0x0000	CH0 Auto-2; n+1	CH1 Auto-2	CH0 Auto-2; n+1	n+2
	Continued Operation	Auto-2	0x0000	CH1 Auto-2; n+2	CH2 Auto-2	CH0 Auto-2; n+2	n+3
	Continued Operation	Auto-2	0x0000	CH2 Auto-2; n+3	CH3 Auto-2	CH0 Auto-2; n+3	n+4
	Continued Operation	Auto-2	0x0000	CH3 Auto-2; n+4	CH4 Auto-2	CH0 Auto-2; n+4	n+5
	Continued Operation	Auto-2	0x0000	CH4 Auto-2; n+5	CH5 Auto-2	CH0 Auto-2; n+5	n+6
	Continued Operation	Auto-2	0x0000	CH5 Auto-2; n+6	CH6 Auto-2	CH0 Auto-2; n+6	n+7
	Continued Operation	Auto-2	0x0000	CH6 Auto-2; n+7	CH7 Auto-2	CH0 Auto-2; n+7	n+8
	Continued Operation	Auto-2	0x0000	CH7 Auto-2; n+8	CH8 Auto-2	CH0 Auto-2; n+8	n+9
	Continued Operation	Auto-2	0x0000	CH8 Auto-2; n+9	CH9 Auto-2	CH0 Auto-2; n+9	n+10
	Continued Operation	Auto-2	0x0000	CH9 Auto-2; n+10	CH10 Auto-2	CH0 Auto-2; n+10	n+11
	Continued Operation	Auto-2	0x0000	CH10 Auto-2; n+11	CH11 Auto-2	CH0 Auto-2; n+11	n+12
	Continued Operation	Auto-2	0x0000	CH11 Auto-2; n+12	CH12 Auto-2	CH0 Auto-2; n+12	n+13
	Continued Operation	Auto-2	0x0000	CH12 Auto-2; n+13	CH13 Auto-2	CH0 Auto-2; n+13	n+14
	Continued Operation	Auto-2	0x0000	CH13 Auto-2; n+14	CH14 Auto-2	CH0 Auto-2; n+14	n+15
	Continued Operation	Auto-2	0x0000	CH14 Auto-2; n+15	CH15 Auto-2	CH0 Auto-2; n+15	n+16
	Continued Operation	Auto-2	0x0000	CH15 Auto-2; n+16	CH0 Auto-2	CH0 Auto-2; n+16	n+17

Also, I am not entirely sure that the SPI write to 0x3C00 mentioned above is required, because the datasheet states in Figure 55, Frame 'n' that "DI10 = x. Device automatically resets to channel 0".

Can you confirm that the sequence below is also valid ... I just removed the first Auto-2 Mode Register command:

Register	Action (For Next Frame)	Mode	SDI SPI Command	Sample and Convert Channel; Frame	MUX Channel Selected	SDO; Frame	Frame
GPIO Program Register	Reset Device	Manual	0x4200	N/A	CH0 Manual	Don't Care	n-2
Auto-2 Program Register	Set Last Channel	Manual	0x93C0	CH0 Manual; n-2	CH0 Manual	Don't Care	n-1
Auto-2 Mode Register	Auto-2 Mode; Increment Channel Mode	Auto-2	0x3800	CH0 Manual; n-1	CH0 Auto-2	CH0 Manual; n-1	n
Mode Control Register	Continued Operation	Auto-2	0x0000	CH0 Auto-2; n	CH1 Auto-2	CH0 Auto-2; n	n+1
	Continued Operation	Auto-2	0x0000	CH1 Auto-2; n+1	CH2 Auto-2	CH0 Auto-2; n+1	n+2
	Continued Operation	Auto-2	0x0000	CH2 Auto-2; n+2	CH3 Auto-2	CH0 Auto-2; n+2	n+3
	Continued Operation	Auto-2	0x0000	CH3 Auto-2; n+3	CH4 Auto-2	CH0 Auto-2; n+3	n+4
	Continued Operation	Auto-2	0x0000	CH4 Auto-2; n+4	CH5 Auto-2	CH0 Auto-2; n+4	n+5
	Continued Operation	Auto-2	0x0000	CH5 Auto-2; n+5	CH6 Auto-2	CH0 Auto-2; n+5	n+6
	Continued Operation	Auto-2	0x0000	CH6 Auto-2; n+6	CH7 Auto-2	CH0 Auto-2; n+6	n+7
	Continued Operation	Auto-2	0x0000	CH7 Auto-2; n+7	CH8 Auto-2	CH0 Auto-2; n+7	n+8
	Continued Operation	Auto-2	0x0000	CH8 Auto-2; n+8	CH9 Auto-2	CH0 Auto-2; n+8	n+9
	Continued Operation	Auto-2	0x0000	CH9 Auto-2; n+9	CH10 Auto-2	CH0 Auto-2; n+9	n+10
	Continued Operation	Auto-2	0x0000	CH10 Auto-2; n+10	CH11 Auto-2	CH0 Auto-2; n+10	n+11
	Continued Operation	Auto-2	0x0000	CH11 Auto-2; n+11	CH12 Auto-2	CH0 Auto-2; n+11	n+12
	Continued Operation	Auto-2	0x0000	CH12 Auto-2; n+12	CH13 Auto-2	CH0 Auto-2; n+12	n+13
	Continued Operation	Auto-2	0x0000	CH13 Auto-2; n+13	CH14 Auto-2	CH0 Auto-2; n+13	n+14
	Continued Operation	Auto-2	0x0000	CH14 Auto-2; n+14	CH15 Auto-2	CH0 Auto-2; n+14	n+15
	Continued Operation	Auto-2	0x0000	CH15 Auto-2; n+15	CH0 Auto-2	CH0 Auto-2; n+15	n+16

over 5 years ago

0 Keith Nicholas over 5 years ago

TI__Mastermind 36040 points

Hi Eric,

The above sequence looks correct at first pass. I will take a closer look at both sequences and get back to you by end of business tomorrow.

Thanks,
Keith N.

0 Keith Nicholas over 5 years ago in reply to Keith Nicholas

TI__Mastermind 36040 points

Hi Eric,

The first sequence should work as expected. For frames n+1 through n+16, you can also write 0x3800 on SDI, or 0x0000 which will repeat the auto-2 command.

You are correct; when you enter auto-2 mode, the device will automatically reset to channel 0, so you do not need to explicitly set DI10 bit in the mode control register for auto-2. However, in either case there is a two cycle delay from the time the MUX is set to channel 0 until you get the conversion result.

In the second sequence, you enter auto-2 mode in frame n. Per Figure 56 in the datasheet, you will not get the conversion results until 2 frames later, or frame n+2 in your above example. The sequence you have now will give conversion results for CH0 in frames n, n+1, and n+2. Frame n+3 will be CH1, and frame n+16 will be CH14. You still need to add one additional frame to get the conversion results of CH15, as per your first sequence above.

Please let me know if you have additional questions.

Regards, Keith N.

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ADS7953-Q1: Auto-2 Mode Sequence