Datasheet

FDS 6531/6532 005 Data Sheet 71M6531D/F-71M6532D/F
Rev 2 57
To facilitate transition to SLEEP mode, which is useful when an unprogrammed IC is mounted on a PCB
with a battery installed, the production test programs the following six-byte sequence into the flash loca-
tion starting at address 0x00000: 0x74 - 0x40 - 0x90 - 0x20 - 0xA9 - 0xF0. This sequence decodes to the
following assembler code:
0000: 7440 MOV A,#40 ; set bit 6 in accumulator
0002: 9020A9 MOV DPTR,#20A9 ; point to I/O RAM address 0x20A9
0005: F0 MOVX @DPTR,A ; set bit 6 (sleep) in 0x20A9
Transitions from both LCD and SLEEP mode are initiated by the wake-up timer timeout conditions or
pushbutton events. When the PB pin is pulled high (pushbutton is pressed), the IE_PB interrupt flag (SFR
0xE8[4]) is set, and when the wake-up timer times out, the IE_WAKE interrupt flag (SFR 0xE8[5]) is set.
In the absence of system power, if the voltage margin for the LDO regulator providing 2.5 V to the internal
circuitry becomes too low to be safe, the part automatically enters SLEEP mode (BAT_OK false). The bat-
tery voltage must stay above 3 V to ensure that BAT_OK remains true. Under this condition, the
71M6531 stays in SLEEP mode, even if the voltage margin for the LDO improves (BAT_OK true). Table
52 shows the circuit functions available in each operating mode.
Table 52: Available Circuit Functions
Circuit Function
System Power
Battery Power (Nonvolatile Supply)
MISSION BROWNOUT LCD SLEEP
CE
Yes
–
–
–
CE Data RAM
Yes
Yes
–
–
FIR
Yes
–
–
–
Analog circuits
Yes
–
–
–
MPU clock rate
From PLL, as
defined by
MPU_DIV[2:0]
28.672 kHz
(7/8 of 32768 Hz)
– –
MPU_DIV[2:0]
Yes
–
–
–
ICE
Yes
Yes
–
–
DIO Pins
Yes
Yes
–
–
Watchdog Timer
Yes
Yes
–
–
LCD
Yes
Yes
Yes
–
EEPROM Interface (2-wire)
Yes
Yes (8 kb/s)
–
–
EEPROM Interface (3-wire)
Yes
Yes (16 kb/s)
–
–
UART
Yes
300 bd
–
–
Optical TX modulation
Yes
–
–
–
Flash Read
Yes
Yes
–
–
Flash Page Erase
Yes
Yes
–
–
Flash Write
Yes
–
–
–
RAM Read and Write
Yes
Yes
–
–
Wakeup Timer
Yes
Yes
Yes
Yes
OSC and RTC
Yes
Yes
Yes
Yes
XRAM data preservation
Yes
Yes
–
–
V3P3D voltage output pin
Yes
Yes
–
–
GPO – GP7 registers
Yes
Yes
Yes
Yes
– indicates not active
2.3.1 BROWNOUT Mode
In BROWNOUT mode, most non-metering digital functions are active (as shown in Table 52), including
ICE, UART, EEPROM, LCD and RTC. In BROWNOUT mode, a low bias current regulator will provide
2.5 Volts to V2P5 and V2P5NV. The regulator has an output called BAT_OK to indicate that it has sufficient
overhead. When BAT_OK = 0, the part will enter SLEEP mode. From BROWNOUT mode, the processor