
III PERIPHERAL BLOCK: 8-BIT PROGRAMMABLE TIMERS
S1C33T01 FUNCTION PART
EPSON
B-III-3-1
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.
Data
bus
8-bit reload data register (RLDx)
8-bit down counter
Control registers
Control circuit
Data buffer (PTDx)
Underflow
Reload
Clock output
Underflow signal output
Underflow
interrupt
Interrupt
controller
Prescaler
Clock
generator
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
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/
T8UF0
I/O I/O port / 16-bit timer 0 event counter
input / 8-bit timer 0 output / DST0 output
CFP10(D0)/P1 function select register (0x402D4)
CFEX1(D1)/Port function extension register (0x402DF)
P11/EXCL1/
T8UF1
I/O I/O port / 16-bit timer 1 event counter
input / 8-bit timer 1 output / DST1 output
CFP11(D1)/P1 function select register (0x402D4)
CFEX1(D1)/Port function extension register (0x402DF)
P12/EXCL2/
T8UF2
I/O I/O port / 16-bit timer 2 event counter
input / 8-bit timer 2 output / DST2 output
CFP12(D2)/P1 function select register (0x402D4)
CFEX0(D0)/Port function extension register (0x402DF)
P13/EXCL3/
T8UF3
I/O I/O port / 16-bit timer 3 event counter
input / 8-bit timer 3 output / DPCO output
CFP13(D3)/P1 function select register (0x402D4)
CFEX1(D1)/Port function extension register (0x402DF)
P50/
T8UF4
I/O I/O port / 8-bit timer 4
CFP50(D0)/P5 function select register (0x40303)
P51/
T8UF5
I/O I/O port / 8-bit timer 5
CFP51(D1)/P5 function select register (0x40303)
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
The pins used with channels 0 through 3 of the 8-bit programmable timers are shared function I/O port pins.
They share functions as event counter inputs and debug signal outputs for the 16-bit programmable timers.
At cold start, these pins are set up as debug signal output pins (function selection bit CFP1[3:0] = "0" and port
function expansion 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.