
S1C62N33 TECHNICAL HARDWARE
EPSON
I-73
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (SVD Circuit and Heavy Load Protection Function)
When the software changes the mode to the heavy load
protection mode (HVLD = "1")
The heavy load protection mode switches the constant
voltage circuit of the LCD system to the high-stability
mode from the low current consumption mode. Conse-
quently, more current is consumed in the heavy load
protection mode than in the normal mode. Unless it is
necessary, be careful not to set the heavy load protection
mode with the software.
This section explains the timing for when the SVD circuit
writes the result of the source voltage detection to the
SVDDT latch.
Turning the SVD operation ON/OFF is controlled through
the software (HVLD, SVDON). Moreover, when a drop in
source voltage (SVDON = "1") is detected, SVD operation is
periodically performed by the hardware until the source
voltage is recovered (SVDON = "0").
The result of the source voltage detection is written to the
SVDDT latch by the SVD circuit, and this data can be read
out by the software to find the status of the source voltage.
There are three methods, explained below, for executing the
detection operation of the SVD circuit.
(1) Sampling with HVLD set to "1"
When HVLD is set to "1" and SVD sampling executed, the
detection results can be written to the SVDDT latch in
the following two timings.
Immediately after the time for one instruction cycle
has ended immediately after HVLD = "1"
Immediately after sampling in the 2 Hz cycle output by
the clock timer while HVLD = "1"
Consequently, the SVDDT latch data is loaded immedi-
ately after HVLD has been set to "1", and at the same
time the new detection result is written in 2 Hz cycles.
To obtain a stable SVD detection result, the SVD circuit
must be set to ON with at least 100 s. Consequently,
when the CPU system clock is fosc3 in S1C62A33, the
detection result at the timing in above may be invalid
or incorrect. (When performing SVD detection using the
timing in , be sure that the CPU system clock is fosc1.)
Detection timing of
SVD circuit