sx20ac Parallax, Inc., sx20ac Datasheet - Page 30

• Manufacturer Part Number: sx20ac
• Description: Configurable Communications Controllers With Ee/flash Program Memory, In-system Programming Capability And On-chip Debug
• Manufacturer: Parallax, Inc.

Parallax SX20AC/SX28AC
14.0 REGISTER STATES UPON DIFFERENT RESET OPERATIONS
The effect of different reset operation on a register
depends on the register and the type of reset operation.
Some registers are initialized to specific values, some are
left unchanged, some are undefined, and some are
initialized to an unknown value. A register that starts with
Note 1: Watchdog reset during Power Down mode: 00(TO, PD); during Active mode: 01 (TO, PD).
Note
© Parallax Inc.
W
OPTION
MODE
RTCC (01h)
PC (02h)
STATUS (03h)
FSR (04h)
RA/RB/RC Direction
RA/RB/RC Data
Other File Registers
SPRAM
CMP_B
WKPND_B
WKED_B
WKEN_B
ST_B/ST_C
LVL_A/LVL_B/LVL_C
PLP_A/PLP_B/PLP_C
Watchdog Counter
2:
Register
External
reset
Undefined
FFh
0Fh
FFh
Bits 0-2: undefined
Bits 3-4: 11
Bits 5-7: 000
Undefined
FFh
Undefined
Undefined
Bits 0, 6-7: 1
Bits 1-5: undefined
Undefined
FFh
FFh
FFh
FFh
FFh
Undefined
Undefined
Power-On
during
Table 14-1: Register States upon Different Resets
Power
Down
Unchanged
FFh
0Fh
Unchanged
FFh
Bits 0-2: unchanged
Bits 3-4: unchanged
Bits 5-7: 000
Bits 0-6: unchanged
Bit 7: 1
FFh
Unchanged
Unchanged
Bits 0, 6-7: 1
Bits 1-5: undefined
Unchanged
FFh
FFh
FFh
FFh
FFh
Unchanged
Wakeup
mode:
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(TO,
Undefined
FFh
0Fh
Undefined
FFh
Bits 0-4: undefined
Bits 5-7: 000
Bits 0-6: undefined
Bit 7: 1
FFh
Undefined
Undefined
Bits 0, 6-7: 1
Bits 1-5: undefined
Undefined
FFh
FFh
FFh
FFh
FFh
Undefined
an unknown value should be initialized by the software to
a known value; you cannot simply test the initial state and
rely on it starting in that state consistently. Table 14-1
lists the SX registers and shows the state of each register
upon different reset.
Brown-Out
PD);
during
Unchanged
FFh
0Fh
Unchanged
FFh
Bits 0-2: unchanged
Bits 3-4: (Note 1)
Bits 5-7: 000
Bits 0-6: unchanged
Bit 7: 1
FFh
Unchanged
Unchanged
Bits 0, 6-7: 1
Bits 1-5: undefined
Unchanged
FFh
FFh
FFh
FFh
FFh
Unchanged
Active
Watchdog Timer
mode,
Unchanged
Unchanged
FFh
0Fh
Unchanged
FFh
Bits 0-2: unchanged
Bits 3-4: (Note 2)
Bits 5-7: 000
Bits 0-6: unchanged
Bit 7: 1
FFh
Unchanged
Unchanged
Bits 0, 6-7: 1
Bits 1-5: undefined
Unchanged
FFh
FFh
FFh
FFh
FFh
Unchanged
Rev 1.6 11/20/2006
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MCLR
((TO,
PD)