PCA88021 NXP [NXP Semiconductors], PCA88021 Datasheet - Page 16

• Manufacturer Part Number: PCA88021
• Description: ultra low power oscillator with integrated counter for initiating one time password generation
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA8802_1
Product data sheet
9.6.5 Instruction 32k_cmd
9.6.6 Instruction fst_cmd
9.6.7 Instruction set_cmd
Table 7.
The 32.768 kHz enable instruction (32k_cmd) is intended to aid with oscillator
characterization during system development. With this instruction it is possible to obtain a
32.768 kHz clock on the INT pin which may be used for measurement.
This mode does not affect other operation of the chip with the exception of loss of interrupt
output.
The fast mode instruction (fst_cmd) is intended to enable faster system development.
When enabled, the counter will increment once every second instead of once every 32
seconds. Interrupt pulses will also be generated once every second.
When using fst_cmd, data access to the device must be completed within 1 second, if not
then counter increments will be lost. The 1 second period is measured from the ACK cycle
of a valid slave address to the next STOP or repeated START. A repeated START will be
sufficient to allow the counter to increment.
The counter can be set to any value using the set instruction (set_cmd). Partial writing of
the data parameters will result in partial setting of the counter. E.g. if data transfer is
stopped after P1[23:16] is transmitted, then only bit 23 to bit 16 will be updated.
Step Action
To enter power-down
1
2
3
4
5
6
7
To exit power-down
1
2
3
4
5
initiate transfer
send wrt_cmd
enable dvs_cmd
set counter with set_cmd
enable pwd_cmd
end transfer
device is now in a
power-down state
initiate transfer
send wrt_cmd
disable pwd_cmd
disable dvs_cmd
end transfer
Power-down sequence
Rev. 01 — 19 February 2009
Code sequence Note
START condition -
1010 0000
0001 0001
1000 0000
1010 1010
1010 1010
1010 1010
0010 0001
STOP condition
-
START condition -
1010 0000
0010 0000
0001 0000
STOP condition
-
stop the divider
set the counter = AAAAAAh
P1[23:16]
P2[15:8]
P3[7:0]
stop the oscillator
-
-
-
oscillator starts on the ACK cycle of this
instruction
enable the divider again
-
PCA8802
© NXP B.V. 2009. All rights reserved.
Smartcard RTC
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