Datasheet

PCF8523 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6 — 17 September 2013 45 of 78
NXP Semiconductors
PCF8523
Real-Time Clock (RTC) and calendar
8.11.2 START and STOP conditions
Both data and clock lines remain HIGH when the bus is not busy. A HIGH-to-LOW
transition of the data line, while the clock is HIGH, is defined as the START condition (S).
A LOW-to-HIGH transition of the data line, while the clock is HIGH, is defined as the
STOP condition (P) (see Figure 29
).
For this device, a repeated START is not allowed. Therefore, a STOP has to be released
before the next START.
8.11.3 System configuration
A device generating a message is a transmitter; a device receiving a message is the
receiver. The device that controls the message is the master and the devices, which are
controlled by the master, are the slaves.
The PCF8523 can act as a slave transmitter and a slave receiver.
Fig 28. Bit transfer
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Fig 29. Definition of START and STOP conditions
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Fig 30. System configuration
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