CS5460A
30
DS284PP4
4.3 Auto-Boot Mode Using EEPROM
The CS5460A has a MODE pin. When the MODE
pin is set to logic low, the CS5460A is in normal
operating mode, called host mode. This mode de-
notes the normal operation of the part, that has been
described so far. But when this pin is set to logic
high, the CS5460A auto-boot mode is enabled. In
auto-boot mode, the CS5460A is configured to re-
quest a memory download from an external serial
EEPROM. The download sequence is initiated by
driving the RESET pin to logic high. Auto-Boot
mode allows the CS5460A to operate without the
need for a microcontroller. Note that if the MODE
pin is left unconnected, it will default to logic low
because of an internal pull-down on the pin.
4.3.1 Auto-Boot Configuration
Figure 13 shows the typical connections between
the CS5460A and a serial EEPROM for proper au-
to-boot operation. In this mode, CS and SCLK are
driven outputs. SDO is always an output. During
the auto-boot sequence, the CS5460A drives CS
low, provides a clock output on SCLK, and drives
out-commands on SDO. It receives the EEPROM
data on SDI. The serial EEPROM must be pro-
grammed with the user-specified commands and
register data that will be used by the CS5460A to
change any of the default register values (if de-
sired) and begin conversions.
Figure 13 also shows the external connections that
would be made to a calibrator device, such as a PC
or custom calibration board. When the metering
system is installed, the calibrator would be used to
control calibration and/or to program user-speci-
fied commands and calibration values into the EE-
PROM. The user-specified commands/data will
determine the CS5460A’s exact operation, when
the auto-boot initialization sequence is running.
Any of the valid commands can be used.
4.3.2 Auto-Boot Data for EEPROM
This section illustrates what a typical set of code
would look like for an auto-boot sequence. This
code is what would be written into the EEPROM
by the user. In the sequence below, the EEPROM
is programmed so that it will first send out com-
mands that write calibration values to the calibra-
tion registers inside the CS5460A. This is followed
by the commands used to set (write) the desired
Pulse-Rate Register value, and also to un-mask the
CS5460A
EEPROM
/EOUT
/EDIR
MODE
SCK
SDI
SDO
/CS
SCK
SO
SI
/CS
Connector to
Calibrator
VD+
5 K
5 K
Mech. Counter
Stepper Motor
or
Figure 13. Typical Interface of EEPROM to CS5460A
Summary of Contents for CS5460A
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