cs5460 Cirrus Logic, Inc., cs5460 Datasheet - Page 18

• Manufacturer Part Number: cs5460
• Description: Single Phase Bi-directional Power/energy Ic
• Manufacturer: Cirrus Logic, Inc.

3.2 Serial Port Interface
The CS5460’s serial interface consists of four con-
trol lines: CS, SDI, SDO, and SCLK.
CS, Chip Select, is the control line which enables
access to the serial port. If the CS pin is tied to logic
0, the port can function as a three wire interface.
SDI, Serial Data In, is the data signal used to trans-
fer data to the converters.
SDO, Serial Data Out, is the data signal used to
transfer output data from the converters. The SDO
output will be held at high impedance any time CS
is at logic 1. Figure 10 illustrates the serial se-
quence necessary to write to, or read from the serial
port’s buffers.
SCLK, Serial Clock, is the serial bit-clock which
controls the shifting of data to or from the ADC’s
serial port. The CS pin must be held at logic 0 be-
fore SCLK transitions can be recognized by the
port logic. To accommodate opto-isolators SCLK
is designed with a Schmitt-trigger input to allow an
opto-isolator with slower rise and fall times to di-
rectly drive the pin. Additionally, SDO is capable
of sinking or sourcing up to 5 mA to directly drive
an opto-isolator LED. SDO will have less than a
400 mV loss in the drive voltage when sinking or
sourcing 5 mA.
As shown in Figure 10 a transfer of data is always
initiated by sending the appropriate 8-bit command
(MSB first) to the serial port (SDI pin). It is impor-
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tant to note that some commands use information
from the cycle-counter and configuration registers
to perform the function. For those commands it is
important that the correct information is written to
those registers first.
When a command involves a write operation the
serial port will continue to clock in the data bits
(MSB first) on the SDI pin for the next 24 SCLK
cycles. When a read command is initiated the serial
port will start transferring register content bit serial
(MSB first) on the SDO pin for the next 8, 16, or 24
SCLK cycles depending on the command issued.
The micro-controller is allowed to send a new com-
mand while reading register data. The new com-
mand will be acted upon immediately and could
possibly terminate the register read. During the
read cycle, the SYNC0 command (NOP) should be
strobed on the SDI port while clocking the data
from the SDO port.
3.3 Serial Port Initialization
The serial port is initialized to the command mode
whenever a reset is performed or when the port ini-
tialization sequence is completed. The port initial-
ization sequence involves clocking 3 (or more)
SYNC1 command bytes (0xFF) followed by
SYNC0 command byte (0xFE). This sequence
places the chip in the command mode where it
waits until a valid command is received.
CS5460
DS279PP5