pca8802 NXP Semiconductors, pca8802 Datasheet - Page 8

• Manufacturer Part Number: pca8802
• Description: Smartcard Rtc; Ultra Low Power Oscillator With Integrated Counter For Initiating One Time Password Generation
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA8802_1
Product data sheet
9.5.1.1 The writing protocol
9.5.1 Interface protocol
9.4 Pulse generator
9.5 I
An interrupt pulse is available at the INT pin. This pulse is generated once every
32 seconds and could be used to wake up a microcontroller to perform a periodic function
e.g. to calculate and update an LCD display with a new one-time password.
A pulse is generated coincident with the increment of the counter. The new counter value
will be available immediately.
The serial interface is based on the I
advantage of being robust in terms of immunity to electrical noise. Although the PCA8802
does not have the signal filters inside the interface pins, the slave address and
acknowledge hand shaking is nevertheless implemented.
For power saving, the SDA output is push-pull instead of the more traditional open-drain
output. Push-pull prevents the need for power consuming pull-up resistors, but does limit
the operation to point to point only.
The following slave addresses plus a write and read bit are reserved for the PCA8802:
An incorrect slave address will result in the device ignoring all bus data. A STOP or
START condition (see
The writing protocol is shown in
There is no restriction for the order of sending instructions. As many instructions as
needed may be sent in one access. The total duration of one access must not exceed
32 seconds (see
2
Fig 9.
•
•
C-bus interface
write: 1010 0000
read: 1010 0001
Pulse generator
Figure
Rev. 01 — 19 February 2009
Section
12).
9.5.4) will be required before a new transfer can be made.
Figure
counter
2
INT
C-bus protocol. The I
10.
001aaj169
2
C-bus protocol has the
PCA8802
© NXP B.V. 2009. All rights reserved.
Smartcard RTC
8 of 34