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PCF8563 Datasheet(PDF) 11 Page - NXP Semiconductors |
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PCF8563 Datasheet(HTML) 11 Page - NXP Semiconductors |
11 / 32 page ![]() PCF8563_6 © NXP B.V. 2008. All rights reserved. Product data sheet Rev. 06 — 21 February 2008 11 of 32 NXP Semiconductors PCF8563 Real-time clock/calendar 7.7 EXT_CLK test mode A Test mode is available which allows for on-board testing. In such a mode it is possible to set up test conditions and control the operation of the RTC. The Test mode is entered by setting bit TEST1 in control_status_1 register. Then pin CLKOUT becomes an input. The Test mode replaces the internal 64 Hz signal with the signal applied to pin CLKOUT. Every 64 positive edges applied to pin CLKOUT will then generate an increment of one second. The signal applied to pin CLKOUT should have a minimum pulse width of 300 ns and a minimum period of 1000 ns. The internal 64 Hz clock, now sourced from CLKOUT, is divided down to 1 Hz by a 26 divide chain called a pre-scaler. The pre-scaler can be set into a known state by using bit STOP. When bit STOP is set, the pre-scaler is reset to 0 (STOP must be cleared before the pre-scaler can operate again). From a STOP condition, the first 1 second increment will take place after 32 positive edges on CLKOUT. Thereafter, every 64 positive edges will cause a one-second increment. Remark: Entry into EXT_CLK test mode is not synchronized to the internal 64 Hz clock. When entering the Test mode, no assumption as to the state of the pre-scaler can be made. Table 22. Timer_control - Timer control register (address 0Eh) bit description Bit Symbol Value Description 7 TE 0 timer is disabled 1 timer is enabled 6 to 2 x not relevant 1 to 0 TD[1:0] see Table 23 timer source clock frequency select; these bits determine the source clock for the countdown timer; when not in use, TD[1:0] should be set to 11 (1 ⁄ 60 Hz) for power saving Table 23. TD1 and TD0: Timer frequency selection TD1 TD0 TIMER Source clock frequency 0 0 4096 Hz 0 1 64 Hz 10 1 Hz 11 1 ⁄60 Hz Table 24. Timer - Timer value register (address 0Fh) bit description Bit Symbol Value Description 7 to 0 TIMER 00h to FFh countdown value = n; CountdownPeriod n SourceClockFrequency --------------------------------------------------------------- = |
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