Datasheet

ADuC7033
Rev. B | Page 68 of 140
PLLCON Prewrite Key PLLKEY0
Name: PLLKEY0
Address: 0xFFFF0410
Access: Write only
Key: 0x000000AA
Function: PLLCON is a keyed register that requires a
32-bit key value to be written before and after
PLLCON. PLLKEY0 is the prewrite key.
PLLCON Postwrite Key PLLKEY1
Name: PLLKEY1
Address: 0xFFFF0418
Access: Write only
Key: 0x00000055
Function: PLLCON is a keyed register that requires a
32-bit key value to be written before and after
PLLCON. PLLKEY1 is the postwrite key.
PLLCON Register
Name: PLLCON
Address: 0xFFFF0414
Default
Va lu e:
0x00
Access: Read/write
Function: This 8-bit register allows user code
dynamically select the PLL source clock from
three different oscillator sources.
Table 45. PLLCON MMR Bit Designations
Bit Description
31 to 2
Reserved, these bits should be written as 0 by user
code.
1 to 0 PLL Clock Source.
1
00 = lower power, 131 kHz oscillator.
01 = precision 131 kHz oscillator.
10 = external 32.768 kHz crystal.
11 = reserved.
1
If the user code switches MCU clock sources, a dummy MCU cycle should be
included after the clock switch is written to PLLCON.
POWCON Prewrite Key POWKEY0
Name: POWKEY0
Address: 0xFFFF0404
Access: Write only
Key: 0x00000001
Function: POWCON is a keyed register that requires a
32-bit key value to be written before and after
POWCON. POWKEY0 is the prewrite key.
POWCON Postwrite Key POWKEY1
Name: POWKEY1
Address: 0xFFFF040C
Access: Write only
Key: 0x000000F4
Function: POWCON is a keyed register that requires a
32-bit key value to be written before and after
POWCON. POWKEY1 is the postwrite key.
POWCON Register
Name: POWCON
Address: 0xFFFF0408
Default Value: 0x79
Access: Read/write
Function: This 8-bit register allows user code to dynami-
cally enter various low power modes and modify
the CD divider that controls the speed of the
ARM7TDMI core.