Texas Instruments ADS1254, Руководство пользователя

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Circuit Description
3-11 Operation
3.4.4 Firmware and Host Communication
The ADS1254EVM firmware controls the acquisition of data from the
ADS1254 and the clock generation circuitry. It is capable of receiving data from
the ADS1254 at the full data rate, while simultaneously performing averaging.
Communication with the host is performed using TI’s CSR-232 protocol, which
is designed for efficient system control over point-to-point serial links.
CSR-232 is based on IEEE P1212r, the control and status registers draft
standard.
The firmware may be upgraded by the user through the serial port. TI may
periodically make enhancements to the ADS1254EVM firmware; these
upgrades are available on TI’s web site, together with a program for performing
the upgrades.
3.4.5 Power Supply
Power is brought into the board through external power connectors J4 and J5,
battery connector BT1, unregulated power input J1, or through the DSK
connectors J9 and J10. If a wall power adaptor is plugged into J1, the battery
is disconnected.
Power supplied from the battery or through J1 is regulated by voltage
regulators U1, U12, and U2, which provide 5-V digital and analog supplies, and
a 3.3-V digital supply. Power supplied from the external connectors is not
filtered; regulated power of the correct voltages must be supplied to these
connectors. Power from the DSK is filtered and bypassed. Resistors R15 and
R16 limit current in case a DSK is plugged in and the onboard regulators have
not yet shut down.
The board is laid out with separate analog and digital power supplies. Analog
power is 5 V and is supplied from regulator U2, external power connector J5,
or the DSK. 3.3-V digital power is supplied from regulator U12 or the DSK.
When the external power connector J4 is used, it supplies regulator U12.
Only one component on the board, clock generator U13, uses 5-V digital
power. When the DSK is used, this component does not operate; however, this
is of no concern, as the DSK supplies its own clock.