CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (I/O Ports)

4.6.5 Special outputs (CL, FR)

The I/O ports P22 and P23 can be used as special output ports that output CL and FR signals by switching the function with software. Since P22 and P23 are set to I/O port (input mode) at initial reset, when using the special outputs, select the special output function using the EXLCDC register.

The data registers, I/O control registers and pull-up control registers of the ports set in the special output can be used as general purpose registers that do not affect the output.

When "1" is written to the EXLCDC register, P22 is set to the CL output port and P23 is set to the FR output port.

The CL and FR signals are LCD synchronous signal (CL) and LCD flame signal (FR) for externally expanded LCD driver, and are output from the P22 terminal and P23 terminal when the functions are switched by the EXLCDC register.

The following tables show the frequencies of the CL and FR signals.

 

Table 4.6.5.1

CL signal frequency

 

OSC1 oscillation

When 1/8 duty

 

When 1/16 duty

When 1/17 duty

frequency

is selected

 

is selected

is selected

32.768 kHz

512 Hz

 

1,024 Hz

1,024 Hz

 

Table 4.6.5.2

FR signal frequency

 

OSC1 oscillation

When 1/8 duty

 

When 1/16 duty

When 1/17 duty

frequency

is selected

 

is selected

is selected

32.768 kHz

32 Hz

 

32 Hz

30.12 Hz

Refer to Section 4.7, "LCD Driver", for control of the LCD drive duty.

Note: A hazard may occur when the CL signal or FR signal is turned ON or OFF (when the port function is switched).

Figure 4.6.5.1 shows the output waveforms of CL and FR signals.

CL output (P22 terminal) FR output (P23 terminal)

CL output (P22 terminal) FR output (P23 terminal)

CL output (P22 terminal) FR output (P23 terminal)

When 1/17 duty is selected

When 1/16 duty is selected

When 1/8 duty is selected

Fig. 4.6.5.1 Output waveforms of CL and FR signals

S1C63558 TECHNICAL MANUAL

EPSON

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