Epson S1C63558 4.10.5 Interrupt function, 4.10.6 Setting of TOUT output

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Programmable Timer)

4.10.5 Interrupt function

The programmable timer can generate an interrupt due to an underflow of the timer 0 and timer 1. See Figure 4.10.2.1 for the interrupt timing.

An underflow of timer 0 and timer 1 sets the corresponding interrupt factor flag IPT0 (timer 0) or IPT1 (timer 1) to "1", and generates an interrupt. The interrupt can also be masked by setting the corresponding interrupt mask register EIPT0 (timer 0) or EIPT1 (timer 1). However, the interrupt factor flag is set to "1" by an underflow of the corresponding timer regardless of the interrupt mask register setting.

4.10.6 Setting of TOUT output

The programmable timer can generate a TOUT signal due to an underflow of timer 0 or timer 1. The TOUT signal is generated by dividing the underflows in 1/2. It is possible to select which timer's underflow is to be used by the TOUT output channel selection register CHSEL. When "0" is written to the CHSEL register, timer 0 is selected and when "1" is written, timer 1 is selected.

Figure 4.10.6.1 shows the TOUT signal waveform when the channel is changed.

CHSEL 0 1

Timer 0 underflow

Timer 1 underflow

TOUT output (R02)

Fig. 4.10.6.1 TOUT signal waveform at channel change

The TOUT signal can be output from the R02 output port terminal. Programmable clocks can be supplied to external devices.

Figure 4.10.6.2 shows the configuration of the output port R02.

Data bus

TOUT

Register

PTOUT

Register	R02
R02	(TOUT)

Register

R02HIZ

Fig. 4.10.6.2 Configuration of R02

The output of a TOUT signal is controlled by the PTOUT register. When "1" is written to the PTOUT register, the TOUT signal is output from the R02 output port terminal and when "0" is written, the terminal goes to a high (VDD) level. However, the data register R02 must always be "1" and the high impedance control register R02HIZ must always be "0" (data output state).

Since the TOUT signal is generated asynchronously from the PTOUT register, a hazard within 1/2 cycle is generated when the signal is turned ON and OFF by setting the register.

Figure 4.10.6.3 shows the output waveform of the TOUT signal.

R02HIZ register		Fix at "0"
R02 register
		Fix at "1"
PTOUT register "0"
	"1"		"0"
TOUT output

Fig. 4.10.6.3 Output waveform of the TOUT signal

S1C63558 TECHNICAL MANUAL EPSON 69