Analog Input on
Channel Ax
Analog Input on
Channel Bv
ADC Clock
Sample and Hold
SH Pulse
tSH
tdschA0_n
tdschB0_n
tdschB0_n+1
Sample n Sample n+1 Sample n+2
tdschA0_n+1
td(SH)
ADC Event Trigger from
EV or Other Sources
SMODE Bit
SM320F2812-HT
SGUS062A–JUNE 2009 –REVISED APRIL 2010
www.ti.com
6.29.7 Simultaneous Sampling Mode (Dual-Channel) (SMODE = 1)

In simultaneous mode, the ADC can continuously convert input signals on any one pair of channels

(A0/B0 to A7/B7). The ADC can start conversions on event triggers from the Event Managers (EVA/EVB),

software trigger, or from an external ADCSOC signal. If the SMODE bit is 1, the ADC does conversions on

two selected channels on every Sample/Hold pulse. The conversion time and latency of the Result

register update are explained below. The ADC interrupt flags are set a few SYSCLKOUT cycles after the

Result register update. The selected channels are sampled simultaneously at the falling edge of the

Sample/Hold pulse. The Sample/Hold pulse width can be programmed to be 1 ADC clock wide (minimum)

or 16 ADC clocks wide (maximum).

NOTE

In Simultaneous mode, the ADCIN channel pair select has to be A0/B0, A1/B1, ..., A7/B7,

and not in other combinations (such as A1/B3, etc.).

Figure 6-40. Simultaneous Sampling Mode Timing

Table 6-51. Simultaneous Sampling Mode Timing(1)
AT 25-MHz ADC
SAMPLE n SAMPLE n + 1 CLOCK, REMARKS
tc(ADCCLK) = 40 ns
Delay time from event
td(SH) 2.5tc(ADCCLK)
trigger to sampling
Sample/Hold (1 + Acqps) × Acqpsvalue = 0–15
tSH 40 ns with Acqps = 0
width/Acquisition Width tc(ADCCLK) ADCTRL1[8:11]
Delay time for first result
td(schA0_n) to appear in Result 4tc(ADCCLK) 160 ns
register
Delay time for first result
td(schB0_n) to appear in Result 5tc(ADCCLK) 200 ns
register
Delay time for successive (3 + Acqps) ×
td(schA0_n+1) results to appear in Result 120 ns
tc(ADCCLK)
register
(1) Not production tested.
140 Electrical Specifications Copyright © 2009–2010, Texas Instruments Incorporated
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