III PERIPHERAL BLOCK: 8-BIT PROGRAMMABLE TIMERS

A-1

III-3 8-BIT PROGRAMMABLE TIMERS

Configuration of 8-Bit Programmable Timer

The Peripheral Block contains six channels of 8-bit programmable timers (timers 0 to 5).

Figure 3.1 shows the structure of the 8-bit programmable timer.

Clock

Prescaler

generator

 

 

 

Reload

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Clock output

 

 

 

Underflow

 

 

 

 

 

 

Control circuit

 

Underflow signal output

 

 

 

 

 

 

 

 

Underflow Interrupt

interrupt controller

8-bit reload data register (RLDx)

8-bit down counter

Data bus

Data buffer (PTDx)

 

Control registers

 

Figure 3.1 Structure of 8-Bit Programmable Timer

Each timer consists of an 8-bit presentable counter and can output a clock generated by the counter's underflow signal to the internal peripheral circuits or external devices. The output clock cycle can be selected from a wide range of cycles by setting the preset data that can be set in the software and the input clock in the prescaler.

Output Pins of 8-Bit Programmable Timers

The underflow signals of 8-bit programmable timers 0 to 3 can be output to external devices.

Table 3.1 shows the pins that are used to output the underflow signals of the 8-bit programmable timers to external devices.

Table 3.1 Output Pins of 8-Bit Programmable Timers

Pin name

I/O

Function

Function select bit

P10/EXCL0/

I/O

I/O port / 16-bit timer 0 event counter

CFP10(D0)/P1 function select register (0x402D4)

T8UF0

 

input / 8-bit timer 0 output / DST0 output

CFEX1(D1)/Port function extension register (0x402DF)

P11/EXCL1/

I/O

I/O port / 16-bit timer 1 event counter

CFP11(D1/P1 function select register (0x402D4)

T8UF1

 

input / 8-bit timer 1 output / DST1 output

CFEX1(D1)/Port function extension register (0x402DF)

P12/EXCL2/

I/O

I/O port / 16-bit timer 2 event counter

CFP12(D2/P1 function select register (0x402D4)

T8UF2

 

input / 8-bit timer 2 output / DST2 output

CFEX0(D0)/Port function extension register (0x402DF)

P13/EXCL3/

I/O

I/O port / 16-bit timer 3 event counter

CFP13(D3/P1 function select register (0x402D4)

T8UF3

 

input / 8-bit timer 3 output / DPCO output

CFEX1(D1)/Port function extension register (0x402DF)

T8UFx (output pin of the 8-bit programmable timer)

This pin outputs a clock divided in each 8-bit programmable timer. The pulse width is equal to that of input clock of the 8-bit programmable timer (prescaler output). Therefore, the pulse width varies according to the prescaler setting.

How to set the output pins of the 8-bit programmable timer

All pins used by the 8-bit programmable timers are shared with I/O ports, event counter inputs of the 16-bit programmable timers and debug signal outputs. At cold start, all these pins are set for the debug signal outputs (function select bit CFP1[3:0] = "0", port extended function bit CFEX[1:0] = "1"). When using the clock output function of the 8-bit programmable timer, write "0" to the port extended function bit CFEXx and write "1" to the function select bit CFP1x for the corresponding pin.

Then, after setting the above, write "1" to the I/O port's I/O control bit IOC1x (D[3:0]) / P1 I/O control register (0x402D6) to set to output mode. In input mode, the pin functions as the 16-bit programmable timer's event counter input and cannot be used to output a clock of the 8-bit programmable timer. At cold start, the register is set to input mode. At hot start, the register retains its status from prior to the reset.

B-III

8TM

S1C33L03 FUNCTION PART

EPSON

B-III-3-1