Control Of Svd Circuit - Epson 0C88832 Technical Manual

Reset function at low voltage detection
To avoid CPU runaway due to a supply voltage
drop, an initial reset function when the supply
voltage drops to level 0 or less can be selected by
the mask option.
The SVD circuit shifts to continuous sampling
status when it detects level 0 (SVD3–SVD0 = 0000B)
four successive times. At this time, the internal
initial reset signal is generated. The reset status
continues until the supply voltage returns to level 2
(SVD3–SVD0 = 0010B) or higher.
Supply voltage
Internal initial reset
SVDON(R)
SVD3
SVD2
SVD1
SVD0

5.13.3 Control of SVD circuit

Table 5.13.3.1 shows the SVD circuit control bits.
Address Bit Name
00FF12 D7 –
D6 –
D5 SVDSP
D4 SVDON
D3 SVD3
D2 SVD2
D1 SVD1
D0 SVD0
*1 After initial reset, this status is set "1" until conclusion of hardware first sampling.
*2 Initial values are set according to the supply voltage detected at first sampling by hardware.
Until conclusion of first sampling, SVD0–SVD3 data are undefined.
E0C88832/88862 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (SVD Circuit)
Level 2
Level 0
4 sec
Fig. 5.13.2.3 Timing chart of the initial reset signal generation
Table 5.13.3.1 SVD circuit control bits
Function
–
–
SVD auto-sampling control
SVD continuous sampling control/status
SVD detection level
SVD3 SVD2 SVD1 SVD0
1 1 1 1
1 1 1 0
: : : :
0 0 0 0
When the reset status is canceled by the restoration
of the supply voltage, the SVD circuit returns to its
previous status. Continuous sampling status
continues in case of the previous status was
continuous sampling. Then CPU starts the reset
exception processing.
Figure 5.13.2.3 shows the timing chart of the initial
reset signal generation. (Example when using 1/4
Hz auto-sampling.)
Reset status
1
–
–
On
R
Busy
W
On
Detection level
Level 15
Level 14
:
Level 0
EPSON
0 SR R/W Comment
–
– Constantry "0" when
–
– being read
0 R/W
Off These registers are
reset to "0" when
→
R/W
Ready 1 0*1 SLP instruction
0
Off is executed.
X R
*2
X R
X R
X R
111