500-003111-000
4-5
4.3 INITIALIZATION
When SYSTEM RESET is applied to the board, the Control Register and
all converter flags are cleared to the LOW state ("0"). The clearing process is
sequential and a delay of at least 50 µs should be allowed before attempting to
control the board after a RESET has occurred. An independent BOARD RESET
can be generated by setting the BOARD RESET control bit to "1."
4.4
ANALOG INPUT MODES
Control of the analog input multiplexer configuration is provided by the
three MODE selection bits: D8, D9, and D10 in the CSR. Table 4.4-1 lists the
control codes for the available modes. Each mode is summarized here, and then it
is described in detail in the section in which the mode is applied.
ZEROED INPUTS: Each input multiplexer is provided with a test input. In the
ZEROED INPUTS mode, all test inputs are grounded to signal return (zero signal)
on the board. This provides a zero reference for the autozero operations.
P2 DIFFERENTIAL: P2 input channels are configured as differential input pairs.
CSR control bits D0 through D3 select one of 16 input channels. P3 inputs are
configured as 16 single-ended channels.
P2 SINGLE-ENDED: P2 input channels are configured as single-ended inputs. CSR
control bits D0 through D4 select one of 32 input channels. P3 inputs are configured
as 16 single-ended channels.
POSITIVE REFERENCE: The on-board positive voltage reference is selected,
either for autogain adjustment operations, or for board-level self-test.
NEGATIVE REFERENCE: The on-board negative voltage reference is selected for
bipolar autogain adjustments.
ANALOG OUTPUT CHAN 00: Analog output channel "00" is connected to the test
bus which can be routed through any of the P2 or P3 input multiplexers for
loopback testing.
ANALOG OUTPUT CHAN 01: Analog output channel "01" is connected to the test
bus for loopback testing.
RESERVED: This mode applies signal return (zero) to the test bus.
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