Datasheet

AD2S1200
Rev. 0 | Page 12 of 24
ABSOLUTE POSITION AND VELOCITY OUTPUT
The angular position and angular velocity are represented by
binary data and can be extracted either via a 12-bit parallel
interface or a 3-wire serial interface that operates at clock rates
up to 25 MHz. The chip select pin,
CS
, must be held low to
enable the device. Angular position and velocity can be selected
using a dedicated polarity input,
RDVEL
.
SOE
Input
The serial output enable pin,
SOE
, is held high to enable the
parallel interface. The
SOE
pin is held low to enable the serial
interface, which places pins (DB0–DB9) in the high impedance
state, while DB11 is the serial output (SO), and DB10 is the
serial clock input (SCLK).
Data Format
The digital angle signal represents the absolute position of the
resolver shaft as a 12-bit unsigned binary word. The digital
velocity signal is a 12-bit twos complement word, which
represents the velocity of the resolver shaft rotating in either a
clockwise or a counterclockwise direction.
Finally, the
RD
input is used to read the data from the output
register and to enable the output buffer. The timing
requirements for the read cycle are illustrated in Figure 7.
SAMPLE
Input
Data is transferred from the position and velocity integrators
respectively to the position and velocity registers following a
high to low transition of the
SAMPLE
signal. This pin must be
held low for at least t
1
ns to guarantee correct latching of the
data.
RD
should not be pulled low before this time. Also, a
rising edge of
SAMPLE
resets the internal registers that contain
the minimum and maximum magnitude of the monitor signal.
PARALLEL INTERFACE
The angular position and angular velocity are available on the
AD2S1200 in two 12-bit registers, which can be accessed via the
12-bit parallel port. The parallel interface is selected holding the
SOE
pin high. Data is transferred from the velocity and position
integrators, respectively, to the position and velocity registers
following a high-to-low transition on the
SAMPLE
pin. The
RDVEL
polarity pin selects which register from the position or
the velocity registers is transferred to the output register. The
CS
pin must be held low to transfer the selected data register to the
output register. Finally, the
RD
input is used to read the data
from the output register and to enable the output buffer. The
timing requirements for the read cycle are shown in Figure 7.
SAMPLE
Input
Data is transferred from the position and velocity integrators,
respectively, to the position and velocity registers following a
high-to-low transition on the
SAMPLE
signal. This pin must be
held low for at least t
1
ns to guarantee correct latching of the
data.
RD
should not be pulled low before this time since data
would not be ready. The converter will continue to operate
during the read process. Also, a rising edge of
SAMPLE
resets
the internal registers that contain the minimum and maximum
magnitude of the monitor signal.
CS
Input
The device will be enabled when
CS
is held low.
RDVEL
Input
RDVEL
input is used to select between the angular position and
velocity registers as shown in Figure 7.
RDVEL
is held high for
angular position and low for angular velocity. The
RDVEL
pin
must be set (stable) at least t
4
ns before the
RD
pin is pulled low.
RD
Input
The 12-bit data bus lines are normally in a high impedance
state. The output buffer is enabled when
CS
and
RD
are held
low. A falling edge of the
RD
signal transfers data to the output
buffer. The selected data is made available to the bus to be read
within t
6
ns of the
RD
pin going low. The data pins will return to
high impedance state when the
RD
returns to high state, within
t
7
ns. If the user is reading data continuously,
RD
can be
reapplied a minimum of t
5
ns after it was released.