Maxim Integrated High-Speed Microcontroller - Manual (Page 34)

High-Speed Microcontroller User’s Guide
Rev: 062210 34 of 176
BGS
Bit 0 Bandgap Select. This bit enables/disables the bandgap reference during Stop mode.
Disabling the bandgap reference provides significant power savings in Stop mode, but
sacrifices the ability to perform a power-fail interrupt or power-fail reset while stopped.
This bit can only be modified with a Timed Access procedure. The state of this bit will be
undefined on devices that do not incorporate a bandgap reference.
0 = The bandgap reference is disabled in Stop mode but will function during normal
operation. V
CC
must fall below 0.4V to cause a reset when this bit is 0.
1 = The bandgap reference will operate in Stop mode.
4.2.18 RTC Trim Register (TRIM)
7 6 5 4 3 2 1 0
SFR 96h E4K X12/ 6 TRM2 TRM2 TRM1 TRM1 TRM0 TRM0
RT-* RT-* RT-* RT-* RT-* RT-* RT-* RT-*
R = Unrestricted Read, W = Unrestricted Write, -n = Value after Reset, * = See description
E4K
Bit 7 External 4096Hz RTC Signal Enable. This bit enables the output of a 4096Hz signal
on pin P1.7 derived from the RTC. Setting this bit overrides any other function of the
pin. It is used for adjusting the frequency of the 32.768kHz RTC crystal oscillator
using the trim bits. This bit is cleared to 0 after any reset, including a no-battery reset.
0 = Calibration function disabled. P1.7 pin will function per the normal pin description.
1 = 4096Hz signal output on P1.7
X12/ 6
Bit 6
RTC Crystal Capacitance Select. This bit selects the internal loading capacitance of the
RTC crystal amplifier. This bit is set to 1 after a no-battery reset, and unchanged by all
other forms of reset.
0 = RTC loading is set for 6pF crystal.
1 = RTC loading is set for 12.5pF crystal.
TRM2
Bit 5 RTC Trim Bit 2. This bit controls the relative adjustment of the RTC internal capacitance.
It is used to calibrate the RTC oscillator frequency. This bit is set to 1 after a no-battery
reset, and unchanged by all other forms of reset.
TRM2
Bit 4
RTC Inverted Trim Bit 2. This bit controls the relative adjustment of the RTC internal
capacitance. It is used to calibrate the RTC oscillator frequency. This bit is set to 1 after a
no-battery reset, and unchanged by all other forms of reset.
TRM1
Bit 3 RTC Trim Bit 1. This bit controls the relative adjustment of the RTC internal capacitance.
It is used to calibrate the RTC oscillator frequency. This bit is set to 0 after a no-battery
reset, and unchanged by all other forms of reset.
TRM1
Bit 2
RTC Inverted Trim Bit 1. This bit must always be set to the complement of the TRM1
bit. Incorrectly writing this bit will default bits
TRIM .7, TRIM .5-0 to their no-battery reset
value. This bit is cleared to 1 after a no-battery reset, and unchanged by all other forms of
reset.
TRM0
Bit 1 RTC Trim Bit 0. This bit controls the relative adjustment of the RTC internal capacitance.
It is used to calibrate the RTC oscillator frequency. This bit is set to 0 after a no-battery
reset, and unchanged by all other forms of reset.
TRM0
Bit 0
RTC Inverted Trim Bit 0. This bit must always be set to the complement of the TRM0
bit. Incorrectly writing this bit will default bits
TRIM .7, TRIM .5-0 to their no-battery reset
value. This bit is cleared to 1 after a no-battery reset, and unchanged by all other forms of
reset.