Texas Instruments TMS320F2802 User Manual
Page 129
Analog Input on
Channel Ax
Analog Input on
Channel Bx
ADC Clock
Sample and Hold
SH Pulse
t
SH
t
dschA0_n
t
dschB0_n
t
dschB0_n+1
Sample n
Sample n+1
Sample n+2
t
dschA0_n+1
t
d(SH)
ADC Event Trigger from
ePWM or Other Sources
SMODE Bit
,
,
,
SPRS230N – OCTOBER 2003 – REVISED MAY 2012
6.10.7.4 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 ePWM, software trigger, or
from an external ADCSOC signal. If the SMODE bit is 1, the ADC will do 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 will be 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, and so forth).
Figure 6-27. Simultaneous Sampling Mode Timing
Table 6-42. Simultaneous Sampling Mode Timing
AT 12.5 MHz
SAMPLE n
SAMPLE n + 1
ADC CLOCK,
REMARKS
t
c(ADCCLK)
= 80 ns
t
d(SH)
Delay time from event trigger to
2.5t
c(ADCCLK)
sampling
t
SH
Sample/Hold width/Acquisition
(1 + Acqps) *
80 ns with
Acqps value = 0–15
Width
t
c(ADCCLK)
Acqps = 0
ADCTRL1[8:11]
t
d(schA0_n)
Delay time for first result to
4t
c(ADCCLK)
320 ns
appear in Result register
t
d(schB0_n )
Delay time for first result to
5t
c(ADCCLK)
400 ns
appear in Result register
t
d(schA0_n+1)
Delay time for successive results
(3 + Acqps) * t
c(ADCCLK)
240 ns
to appear in Result register
t
d(schB0_n+1 )
Delay time for successive results
(3 + Acqps) * t
c(ADCCLK)
240 ns
to appear in Result register
Copyright © 2003–2012, Texas Instruments Incorporated
Electrical Specifications
129
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