Specifications

8–14 EPSON
SED1240 Series
Fig. 1 shows a timing chart of the serial interface. In case of the SCL signal, extreme care should be taken about terminal
reflection and external noise due to a wiring length. Accordingly, it is recommended to make an operation check.
It is also recommended to periodically refresh the each command write state to prevent a malfunction from being caused
by noise.
Fig. 1 Serial Interface Input Timing
Identification of data bus signals
The SED1240 series identifies each data bus signal by a combination of A0 and WR (E) as shown in Table 3.
Table 3
Chip select
The SED1240 series has chip select pin CS. Only when CS = “L”, the MPU interface is enabled. In the other states than
the chip select state, D0 to D7 and A0, WR, SI, and SCL inputs are invalidated. When an serial input interface is selected,
the shift register and the counter are reset. However, the RES input can be performed regardless of the CS state.
Power Circuit
The power circuit built in the SED1240 series is a low power consumption power circuit that generates a voltage required
for liquid crystal drive, and consists of a boosting circuit, voltage regulating circuit, and voltage follower.
The power circuit capacity is set for a small-scale liquid crystal panel.
In the case of a liquid crystal panel with a large display capacity, the display quality may be remarkably degraded. In this
case, an external power supply is required.
Functional selection is performed by power control commands.
Some parts of the external power supply and the internal power supply can be used together.
Table 4
Note 1: When the boosting circuit is turned off, set the boosting system pins (CAP1+, CAP1–, CAP2+, CAP2–) to
OPEN so that liquid crystal drive voltages may be applied to the V
OUT pin from the outside.
Note 2: When the voltage regulating circuit is not used with the boosting circuit OFF, set the VOUT pin and the
boosting system pins to OPEN and connect the V
5 pin to give liquid crystal drive voltages from the outside.
Note 3: When all the built-in power supplies are turned off, liquid crystal drive voltages V
1, V2, V3, V4, and V5 are
supplied from the outside and set the CAP1+, CAP1–, VSS2 and VOUT pins to OPEN.
D6 (SCL) 1
A0
D7 (SI)
CS
D7 D6 D5 D4 D3 D2 D1 D0 D7
23456781
Common 68 series 80 series
Function
A0 (E) WR
1 1 0 Writes into the RAM and symbol register.
0 1 0 Writes into the internal register (commands)
Boosting Voltage regulat- Voltage External Boosting
circuit ing circuit follower voltage input system pin
●● ●● ●● V
SS2 USE
× ●● ●● V
OUT, VSS2 OPEN
××●● V
5, VSS2 OPEN
×××
V1, V2, V3, V4, V5 OPEN
Note 1
Note 2
Note 3