AS1543/44
Data Sheet - Detailed Description
Power Mode Selection
Control register bits PM1 and PM0 are used to configure the AS1543/44 power mode.
Table 10. Power Mode Selection via Bits PM1 and PM0
PM1
PM0
Mode
Description
In this mode, the AS1543/44 remains in full power mode regardless of the
status of any of the logic inputs. This mode allows the fastest possible
throughput rate.
1
1
Normal Operation
In this mode, the AS1543/44 automatically enters shutdown mode at the end of
each conversion when the control register is updated. Wake-up time from
shutdown is 1µs.
0
X
Auto Shutdown
Note: Ensure that 1µs has elapsed before attempting to perform a valid conver-
sion in this mode.
Sequencer Operation
The setting of control register bits SEQ and SHADOW sets the sequencer operation and also selects the shadow reg-
ister for programming.
Table 11. Sequencer Configuration via Bits SEQ and SHADOW
SEQ
SHADOW
Description
These settings indicate that the sequencer is not used. The analog input
channel selected for each individual conversion is determined by the
contents of the channel address bits ADDR3:ADDR0 (page 14) in each
prior write operation. This mode of operation reflects the normal operation
of a multi-channel ADC (without the sequencer) where each write to the
AS1543/44 specifies the next input channel for conversion (see Figure 28
on page 18).
0
0
These settings select the shadow register for programming. After a write
to the control register, the following write operation will load the contents
of the shadow register. This will program the sequence of channels to be
repeatedly converted each successive valid CSN falling edge (see
Table 12 on page 18 and Figure 29 on page 19).
0
1
Note: The specified input channels need not be consecutive.
With these settings, the sequencer will not be interrupted upon
completion of a write operation. This allows other bits of the control
register (PM1, PM0, WEAK/TRIN, RANGE, CODING and SE/FDN) to be
altered while in a sequence without terminating the cycle.
1
1
0
1
These settings are used in conjunction with the channel address bits
ADDR3:ADDR0 to program continuous conversions on a consecutive
sequence of channels (channel 0 ... channel n) as determined by the
address bits ADDR3:ADDR0 (page 14) of the control register (see Figure
30 on page 20).
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