18
Getting
Started
Flash Memory Size
256KB
Main: Interrupt vector
00FFFFh to 00FF80h
Main: Code memory
047FFFh to 008000h
RAM Size
16KB + 2KB
Application RAM
02400h-063FFh
USB RAM
0023FFh-001C00h
Flash Boot Strap Loader
2KB
Peripherals
4KB
Information Memory
512 Byte
Info A
01980h – 019FFh
Info B
018FFh – 0197Fh
Info C
01880h – 018FFh
Info D
01800h – 0187Fh
5.2
Backup Battery Subsystem
The F6638 device is equipped with the ability to run RTC off a backup battery or capacitor and
provide automatic switching to the secondary source in case the primary power fails.
The oscillator circuitry, select RTC registers and four words of backup memory are by default
powered by the backup source. If there is no backup source connected Jumper JP11 on the
MSP-TS430PZ100 USB target board connects the backup battery pin V
BAT
to the device power
DV
CC
. This connection is required to power the oscillator.
It is also possible to power the oscillator directly from DVcc by disabling the backup system in
software. This is done by setting the BAKDIS and BAKSW bits in the BAKCTL register.
5.3
XT1 Oscillator
The XT1 oscillator on the F6638 device is powered by the backup or secondary battery source.
On exit from a BOR it is required to clear the LOCKIO bits in the BACKCTL register to unlock
XT1 pins for operation. This requirement is unique to the F66xx family and can be done by the
following code.
while(BAKCTL & LOCKIO) // Unlock XT1 pins for operation
BAKCTL &= ~(LOCKIO);
The X430F6638 device is affected by erratum USB7 [refer the device errata sheet]. Due to this
erratum it is required to have a 32.768 KHz crystal populated on XT1 when the USB module is in
use. Note that this erratum will be fixed in the released MSP430F6638 device.
5.4
RTC_B Module
The RTC_B module in the F66xx device family is unique in that it is capable of operation (1)
when the device is in LPM5 (Core is powered down) and (2) When the primary supply Vcc fails.
