6
FN9201.2
March 21, 2008
Theory of Operation
The ISL6296 contains all circuitry required to support battery
pack authentication based on a challenge-response
scheme. It provides a 16-Byte One-Time Programmable
Read-Only Memory (OTPROM) space for the storage of up
to 96-Bit of secret for the authentication and other user
information. A 32-Bit CRC-based hash engine (FlexiHash™)
calculates the authentication result immediately after
receiving a 32-Bit random challenge code. The
communication between the ISL6296 and the host is
implemented through the XSD single-wire communication
bus.
Major functions within the ISL6296 include the following: (as
shown in Figure 3).
• Power-on reset (POR) and a 2.5V regulator to power all
internal logic circuits.
• 16x8-Bit (16-Byte) OTP ROM as shown in Table 8. The
first part (two bytes) contains the device default
configuration (DCFG) information (such as the device
address and the XSD communication speed) and the
default trimming (DTRM) information (such as the internal
oscillator frequency trimming). The second part contains
two groups (12-Byte) of memory that can be
independently locked out for the storage of up to three
sets of secret. The last part provides two additional bytes
of space for general-purpose information.
• Control functions, including master control (MSCR) and
status (STAT) registers (as shown in Table 9), interrupt
generation, and the test-related interface.
• FlexiHash™ engine that includes the 32-Bit CRC-based
hash engine, secret selection register, challenge code
register, and the authentication result register. Table 10
shows all the registers.
• XSD communication bus Interface. The XSD device
address and the communication speed are configured in
the DCFG address in the OTPROM, as given in Table 8.
• Time Base Reference.
The following explain in detail the operation of the ISL6296.
Power-On Reset (POR)
The ISL6296 powers up in Sleep mode. It remains in Sleep
mode until a power-on ‘break’ command is received from the
host through the XSD bus. The initial power-on ’break’ can
be of any pulse width as long as it is wider than the XSD
input deglitch time (20µs). Once the ‘break’ command is
received, the internal regulator is powered up. About 20µs
after the falling edge of the power-on ‘break’, an internal
POR circuit releases the reset to the digital block, and a
POR sequence is started. During the POR sequence, the
ISL6296 initializes itself by loading the default device
configuration information from pre-assigned locations within
the OTP ROM memory. After initialization, a ‘break’
command is returned to the host to indicate that the ISL6296
is ready and waiting for a bus transaction from the host.
Note that the ISL6296 will initiate the power-on sequence
without waiting for the power-on ‘break’ signal to return to
the high state. If the host sends an initial ‘break’ pulse wider
than 60µs, the device-ready ‘break’ returned by the ISL6296
will likely be merged with the pulse sent by the host and,
therefore, may not be detectable. Figure 3 illustrates the
waveforms during the Power-on Reset. Figure 3 (A)
represents the case when the power-on ‘break’ rising edge
occurs after the device starts sending the ‘break’.
Figure 3 (B) represents the case when the power-on ‘break’
finishes before the device sends its ‘break’. The device
break signal is always 1.391 x of the device bit-time (BT, see
XSD Bus Interface section for more details). Either case in
Figure 3 will wake up the device successfully if the device is
in the sleep mode.
NOTE: It is important to keep in mind that a narrow ‘break’ signal will
be taken as a normal bit signal and cause errors, if the device is not
in the sleep mode. For this reason, the narrow power-on ‘break’
signal should be used only if the user has to see the returned ‘break’
signal.
Auto-Sleep
While the ISL6296 is powered up and there is no bus activity
for more than about 1S, the device will automatically return
to Sleep mode. Sleep mode can be entered independent of
whether the XSD bus is held high or low. While the ISL6296
is in Sleep mode, it is recommended that the XSD bus be
held low to eliminate current drain through the XSD-pin
internal pull-down current.
Auto-Sleep mode can be disabled by clearing the ASLP bit
in the MSCR register. By default, Auto-Sleep is always
enabled at power-up and after a soft reset. Auto-sleep
function can be permanently disabled by clearing the 0-00[2]
bit (the ASLP bit in DCFG) during OTP ROM programming.
FIGURE 3. POWER-ON BREAK SIGNAL TO WAKE-UP THE
ISL6296 FROM SLEEP MODE
HOST BREAK
DEVICE BREAK
XSD BUS
WAVEFORM
60µs
TYP
1.391
BT
D
HOST BREAK
DEVICE BREAK
XSD BUS
WAVEFORM
(A) WHEN THE HOST POWER-ON BREAK IS WIDER THAN 60µs.
(B) WHEN THE HOST POWER-ON BREAK IS NARROWER THAN 60µs.
ISL6296
