Cirrus Logic CS5460A - Manual (Page 24)

CS5460A
24 DS487F5
pulse, one of the output pins (either EOUT or ED-
IR) changes state. When the CS5460A must issue
another energy pulse, the other output changes
state. The direction the motor will rotate is deter-
mined by the order of the state changes. When en- ergy is positive, EOUT will lead EDIR such that the
EOUT pulse train will lead the EDIR pulse train by
~1/4 of the periods of these two pulse train signal.
When energy is negative, EDIR will lead EOUT in
a similar manner. See Figure 12.
3.3 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 op-
erating 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 en-
abled. In auto-boot mode, the CS5460A is config-
ured to request 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.
3.3.1 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
EOUT
EDIR
Positive Energy Negative Energy
...
... ...
...
Figure 12. Stepper Motor Format on EOUT and EDIR
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