E0C88832/88862 TECHNICAL MANUAL
EPSON
111
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (SVD Circuit)
■
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.
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.)
Supply voltage
Internal initial reset
SVDON(R)
SVD3
SVD2
SVD1
SVD0
Level 2
Level 0
Reset status
4 sec
Fig. 5.13.2.3 Timing chart of the initial reset signal generation
5.13.3 Control of SVD circuit
Table 5.13.3.1 shows the SVD circuit control bits.
Table 5.13.3.1 SVD circuit control bits
Address Bit
Name
SR R/W
Function
Comment
1
0
00FF12 D7
D6
D5
D4
D3
D2
D1
D0
–
–
SVDSP
SVDON
SVD3
SVD2
SVD1
SVD0
–
–
SVD auto-sampling control
SVD continuous sampling control/status
SVD detection level
Constantry "0" when
being read
These registers are
reset to "0" when
SLP instruction
is executed.
*2
–
–
0
1
→
0*1
0
X
X
X
X
R/W
R/W
R
R
R
R
–
–
On
Busy
On
–
–
Off
Ready
Off
R
W
SVD3
1
1
:
0
SVD2
1
1
:
0
SVD1
1
1
:
0
SVD0
1
0
:
0
Detection level
Level 15
Level 14
:
Level 0
*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.
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