Nxp Semiconductors PCA2125 User Manual

 

 

UM10301_1 

© NXP B.V. 2008. All rights reserved.

The PCA8565 and PCA2125 oscillators operate over a wider temperature range (up to 
125 ºC) and are suitable for use in the harsh environments found within automobiles. 
Power consumption remains low — only 700 nA at 2 V. Serial interface is I

2

C or SPI. 

All the RTCs have ESD protection that exceeds 2000 V HBM per JESD22-A114, 200 V 
MM per JESD22-A115. Charge Device Model values vary from 500 V to 2000 V CDM 
per JESD22-C101. Refer to the datasheet of the respective device. Latch-up testing, 
performed in accordance with JEDEC Standard JESD78, exceeds 100 mA. 

 

 

Table 2 on the next page gives a quick overview of the features, specifications and 
differences between the RTCs dealt with in this User Manual. The PCF8573 which 
belongs to the PCF85x3 family is no longer in production and has thus not been included 
in the table. However, this user manual is useful for this type as well. 

Further there are some derived types from the main types listed in the table with small 
differences in for example delivery form or the number of integrated oscillator capacitors. 
Consult NXP for more details. 
 

Two real time clocks, PCF8583 and PCF8593, have an extraordinary feature. It is the 
event counter mode which can be selected by setting the appropriate bits in the control 
register. In this mode the oscillator is disabled and the oscillator input is switched to a 
high impedance state. This mode can be used to count pulses applied to the oscillator 
input OSCI. There is no crystal in the circuit and OSCO is left open circuit. The event 
counter stores up to 6 digits of data. Events are stored in BCD format. The 6 digits use 
three 8 bit registers (hundredth of a second, seconds, and minutes). D5 is the most 
significant and D0 the least significant digit. Every digit can contain values ranging from 0 
to 9 and thus up to 999 999 events can be stored. 

It is also possible to set an event counter alarm. When this function is enabled, the alarm 
occurs when the event counter registers match the programmed value. In this event the 
alarm flag is set. The inverted value of this flag can be transferred to the interrupt pin by 
setting the alarm interrupt enable in the alarm control register. In this mode the timer 
increments once for every one, one hundred, ten thousand or 1 million events, 
depending on the programmed value of the alarm control register. In all other events, the 
timer functions are as in clock mode. 

Note that immediately following power-on, all internal registers are undefined and must 
be defined by software. It is also possible that upon power-on the device is initially in 
event-counter mode in which event the oscillator will not operate until the correct settings 
are written into the control registers. 

The count value will increment on the falling edge. However, after a new count value has 
been programmed at least one rising edge must have occurred before events will be 
detected on the falling edge.