
741
Chapter 19
RESET Function
User’s Manual U16702EE3V2UD00
19.3 Operation
19.3.1 Reset operation by RESET pin
When a low level is input to the RESET pin, the system is reset, and each hardware unit is initialized.
When the level of the RESET pin is changed from low to high, the reset status is released and the oscil-
lation stabilization timer begins counting (reset value of OSTS register: 2
13
/f
X
). When the OSTS timer
elapses, then the CPU starts program execution.
Note:
Because the V850E/RS1 supports a boot swap function, the firmware uses part of the internal
RAM after the internal system reset is released. Therefore, the contents of some areas (RAM
size is 3FC800H-3FC895H into 10K byte and 3FB000H-3FB095H into 16K byte and 2K byte
down from the uppermost address 3FEFFFH- 3FE7FFH) of the RAM are not retained even
when power-on reset is executed.
Caution:
The on-chip debug mode (flash memory products only) may be set depending on the
pin status after reset has been released. For details, see Chapter 4
”Port Functions”
on page 105 and Chapter 22
”On-Chip Debug Function” on page 767.
Table 19-1:
Hardware Status on RESET Pin Input
Item
During Reset
After Reset
Main clock oscillator (f
X
)
Continues oscillation
Ring-OSC generator
Stops oscillation
Starts oscillation
Peripheral clock (f
XX
to f
XX
/1,024)
Stops operation
Starts operation after oscillation stabili-
zation time (initialized to f
XX
×
4)
Internal system clock (f
CLK
),
CPU clock (f
CPU
)
Stops operation
Starts operation after oscillation stabili-
zation time (initialized to f
XX
×
4)
CPU
Initialized
Program execution starts after oscilla-
tion stabilization time
Watchdog timer 2
Stops operation
Starts operation
Internal RAM
undefined after a reset while power is on or if a data access to RAM (by the
CPU) and a reset input conflict (data corrupted). Otherwise, retains value
immediately before reset input
Note
.
I/O lines (ports/alternate-function
pins)
High impedance
On-chip peripheral I/O registers
Initialized to specified status, OCDM register is set (01H).
Other on-chip peripheral functions Operation stops
Operation can be started after securing
oscillation stabilization time
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