Chapter 1 Hardware Structure
The different types of resets described affect the reset flags in different ways. These flags known
as PDF and TO are located in the status register and are controlled by various microcontroller op-
erations such as the HALT function or Watchdog Timer. The reset flags are shown in the table:
TO
0
u
1
1
²u²
stands for unchanged
PDF
0
u
u
1
RESET Conditions
RES reset during power-on
RES or LVR reset during normal operation
WDT time-out reset during normal operation
WDT time-out reset during HALT
The following table indicates the way in which the various components of the microcontroller are
affected after a power-on reset occurs.
Item
Program Counter
Interrupts
WDT, RTC Interrupt, Time Base
Timer/Event Counter
Input/Output Ports
Stack Pointer
UART
Reset to zero
All interrupts will be disabled
Clear after reset
All Timer Counters will be turned off
All I/O ports will be setup as high
Stack Pointer will point to the top of the stack
UART disabled, TX and RX pins are setup as PC0/PC1
Condition After RESET
The different kinds of reset all affect the internal registers of the microcontroller in different ways.
To ensure reliable continuation of normal program execution after a reset occurs, it is important to
know what condition the microcontroller is in after a particular reset occurs. The following table de-
scribes how each type of reset affects each of the microcontroller internal registers.
HT49R30A-1/HT49C30-1/HT49C30L
Register
MP0
MP1
BP
ACC
PCL
TBLP
TBLH
RTCC
STATUS
INTC0
TMR
TMRC
PA
PB
INTC1
Reset (Power-on)
-
xxx xxxx
-
xxx xxxx
---- ---
0
xxxx xxxx
0000 0000
xxxx xxxx
--
xx xxxx
--
00 0111
--
00 xxxx
-
000 0000
xxxx xxxx
0000 1
---
1111 1111
--
xx xxxx
--
00
--
00
RES or LVR Reset
-
uuu uuuu
-
uuu uuuu
---- ---
0
uuuu uuuu
0000 0000
uuuu uuuu
--
uu uuuu
--
00 0111
--
uu uuuu
-
000 0000
xxxx xxxx
0000 1
---
1111 1111
--
xx xxxx
--
00
--
00
WDT Time-out
(Normal Operation)
-
uuu uuuu
-
uuu uuuu
---- ---
0
uuuu uuuu
0000 0000
uuuu uuuu
--
uu uuuu
--
00 0111
--
1u uuuu
-
000 0000
xxxx xxxx
0000 1
---
1111 1111
--
xx xxxx
--
00
--
00
WDT Time-out
(HALT)
-
uuu uuuu
-
uuu uuuu
---- ---
u
uuuu uuuu
0000 0000
uuuu uuuu
--
uu uuuu
--
uu uuuu
--
11 uuuu
-
uuu uuuu
uuuu uuuu
uuuu u
---
uuuu uuuu
--
uu uuuu
--
uu
--
uu
²u²
stands for unchanged
²x²
stands for unknown
²-²
stands for unimplemented
81
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