GMS81C5108 Datasheet, PDF(46/102 Page) Hynix Semiconductor – HYNIX SEMICONDUCTOR INC. 8-BIT SINGLE-CHIP MICROCONTROLLERS

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GMS81C5108 Datasheet, PDF (46/102 Pages) Hynix Semiconductor – HYNIX SEMICONDUCTOR INC. 8-BIT SINGLE-CHIP MICROCONTROLLERS

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GMS81C5108

11. BASIC INTERVAL TIMER

The GMS81C5108 has one 8-bit Basic Interval Timer that

is free-run and can not stop. Block diagram is shown in

Figure 11-1.

The Basic Interval Timer Register (BITR) is increased ev-

ery internal count pulse which is divided by prescaler.

Since prescaler has divided ratio by 8 to 1024, the count

rate is 1/8 to 1/1024 of the oscillator frequency. After reset,

the BCK bits are all set, so the longest oscillation stabiliza-

tion time is obtained.

It also provides a Basic interval timer interrupt (BITF).

The count overflow of BITR from FFH to 00H causes the

interrupt to be generated. The Basic Interval Timer is con-

trolled by the clock control register (CKCTLR) shown in

Figure 11-2.

Source clock can be selected by lower 3 bits of CKCTLR.

When write â1â to bit BCL of CKCTLR, BITR register is

cleared to â0â and restart to count up. The bit BCL be-

comes â0â automatically after one machine cycle by hard-

ware.

BITR and CKCTLR are located at same address, and ad-

dress 0F4H is read as a BITR, and written to CKCTLR.

fMAINÃ·23 or fSUBÃ·23

fMAINÃ·24 or fSUBÃ·24

fMAINÃ·25 or fSUBÃ·25

fMAINÃ·26 or fSUBÃ·26

fMAINÃ·27 or fSUBÃ·27

fMAINÃ·28 or fSUBÃ·28

fMAINÃ·29 or fSUBÃ·29

fMAINÃ·210 or fSUBÃ·210

source

clock

MUX

8-bit up-counter

BITR

overflow

[0F4H]

clear

Select Input clock 3

fMAIN: main-clock frequency

BCK<2:0>

BCL

fSUB: sub-clock frequency

[0F4H]

CKCTLR

Basic Interval Timer

clock control register

Internal bus line

BITF

Basic Interval Timer Interrupt

Figure 11-1 Block Diagram of Basic Interval Timer

BCK

<2:0>

000

001

010

011

100

101

110

111

Source clock

SCMR[1:0]=

00 or 01

SCMR[1:0]=

10 or 11

fMAINÃ·23

fMAINÃ·24

fMAINÃ·25

fMAINÃ·26

fMAINÃ·27

fMAINÃ·28

fMAINÃ·29

fMAINÃ·210

fSUBÃ·23

fSUBÃ·24

fSUBÃ·25

fSUBÃ·26

fSUBÃ·27

fSUBÃ·28

fSUBÃ·29

fSUBÃ·210

Interrupt (overflow) Period

At fMAIN=4MHz At fSUB=32.768kHz

0.512 ms

1.024

2.048

4.096

8.192

16.384

32.768

65.536

62.5 ms

125.0

250.0

500.0

1000.0

2000.0

4000.0

8000.0

Table 11-1 Basic Interval Timer Interrupt Time

JUNE 2001 Ver 1.0

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