© 2000 Scenix Semiconductor, Inc. All rights reserved. - 29 - www.scenix.com SX18AC/SX20AC/SX28AC/SX18AC75/SX20AC75/SX28AC75 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  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. Table 14-1.  Register States Upon Different Resets Register Power-On Wakeup Brown-out Watchdog Timeout MCLR W Undefined Unchanged Undefined Unchanged Unchanged OPTION FFh FFh FFh FFh FFh MODE 0Fh 0Fh 0Fh 0Fh 0Fh RTCC (01h) Undefined Unchanged Undefined Unchanged Unchanged PC (02h) FFh FFh FFh FFh FFh STATUS (03h) Bits 0-2: Unde-
fined
Bits 3-4: 11
Bits 5-7: 000 Bits 0-2: Un-
changed.
Bits 3-4: Unch.
Bits 5-7: 000 Bits 0-4: Unde-
fined
Bits 5-7: 000 Bits 0-2: Un-
changed
Bits 3-4: (Note 1)
Bits 5-7: 000 Bits 0-2: Un-
changed
Bits 3-4: (Note 2)
Bits 5-7: 000 FSR (04h) Undefined Bits 0-6: Un-
changed
Bit 7: 1 Bits 0-6: Unde-
fined
Bit 7: 1 Bits 0-6: Un-
changed
Bit 7: 1 Bits 0-6: Un-
changed
Bit 7: 1 RA/RB/RC
Direction FFh FFh FFh FFh FFh RA/RB/RC Data Undefined Unchanged Undefined Unchanged Unchanged Other File Registers -
SRAM Undefined Unchanged Undefined Unchanged Unchanged CMP_B Bits 0, 6-7: 1
Bits 1-5: Unde-
fined Bits 0, 6-7: 1
Bits 1-5: Unde-
fined Bits 0, 6-7: 1
Bits 1-5: Unde-
fined Bits 0, 6-7: 1
Bits 1-5: Unde-
fined Bits 0, 6-7: 1
Bits 1-5: Unde-
fined WKPND_B Undefined Unchanged Undefined Unchanged Unchanged WKED_B FFh FFh FFh FFh FFh WKEN_B FFh FFh FFh FFh FFh ST_B/ST_C FFh FFh FFh FFh FFh LVL_A/LVL_B/LVL_C FFh FFh FFh FFh FFh PLP_A/PLP_B/PLP_C FFh FFh FFh FFh FFh Watchdog Counter Undefined Unchanged Undefined Unchanged Unchanged NOTE: 1. Watchdog reset during power down mode: 00 (TO, PD) Watchdog reset during Active mode: 01 (TO, PD) NOTE: 2. External reset during power down mode: 10 (TO, PD)    External reset during Active mode: Unchanged (TO, PD)