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HT45R37-A(28SSOP-A) 参数 Datasheet PDF下载

HT45R37-A(28SSOP-A)图片预览
型号: HT45R37-A(28SSOP-A)
PDF下载: 下载PDF文件 查看货源
内容描述: [Microcontroller, 8-Bit, UVPROM, 12MHz, CMOS, PDSO28]
分类和应用: 可编程只读存储器LTE微控制器光电二极管
文件页数/大小: 100 页 / 666 K
品牌: HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
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HT45R37  
Timer Program Example  
This program example shows how the Timer/Event Counter registers are setup, along with how the interrupts are en-  
abled and managed. Note how the Timer/Event Counter is turned on, by setting bit 4 of the Timer Control Register. The  
Timer/Event Counter can be turned off in a similar way by clearing the same bit. This example program sets the  
Timer/Event Counter to be in the timer mode, which uses the internal system clock as the clock source.  
org 04h  
reti  
; external interrupt vector  
org 0Ch  
jmp tmrint  
:
; Timer/Event Counter 0 interrupt vector  
; jump here when the Timer/Event Counter 0 overflows  
org 20h ; main program  
;internal Timer/Event Counter 0 interrupt routine  
tmrint:  
:
; Timer/Event Counter 0 main program placed here  
:
reti  
:
:
begin:  
;setup Timer 0 registers  
mov a,09bh  
mov tmr0,a;  
mov a,081h  
mov tmr0c,a  
; setup Timer 0 preload value  
; setup Timer 0 control register  
; timer mode and prescaler set to /2  
; setup interrupt register  
mov a,009h  
mov int0c,a  
set tmr0c.4  
; enable master interrupt and timer interrupt  
; start Timer/Event Counter 0 - note mode bits must be previously setup  
C/R to F Converter  
The C/R to F Converter function within the device en-  
ables external resistance and capacitance to be con-  
verted into a frequency. With this function the device has  
a way of measuring external capacitance and resis-  
tance values and can therefore be used in applications  
such as touch switches.  
The Timer A clock source comes from the system clock  
or from the system clock/4, determined by the RCOM  
bits in the RCOCCR register. This clock source deter-  
mines the value in the TMRAL/TMRAH registers. The  
Timer B clock source comes from the external RC oscil-  
lator circuit and therefore determines the value in the  
TMRBL/TMRBL registers. It is a combination of a fixed  
frequency clock source driving Timer A and a varying  
frequency clock source driving Timer B that enables ex-  
ternal resistance and capacitance values to be mea-  
sured.  
C/R to F Operation  
The C/R to F function is implemented using an external  
RC oscillator. A single external reference resistor and  
external reference capacitor are required to be con-  
nected as shown. These components and the internal  
inverter circuits form an oscillator circuit whose fre-  
quency is dependent upon the value of the external ca-  
pacitance and resistance. By using two internal 16-bit  
programmable count-up timers, known as Timer A and  
Timer B, the converted frequency value can be mea-  
sured.  
The OVB bit, in the RCOCR register, decides whether  
Timer A or Timer B overflows. When this happens, the  
RCOCF bit will be set and an external RC oscillation  
converter interrupt occurs. When the C/R to F converter  
causes Timer A or Timer B to overflow, the RCOCON bit  
in the RCOCCR register will be reset to zero and the  
counter will stop counting. Writing initial values to the  
TMRAL/TMRAH and TMRBL/TMRBH registers places  
a start value into Timer A and Timer B. Note that writing  
to the low byte registers, TMRAL and TMRBL, only  
writes the data into a low byte buffer. However writing to  
the high byte registers, TMRAH and TMRBH, will write  
both the high byte values and the low byte buffer values  
directly into the Timer A and Timer B simultaneously.  
The value of the two internal 16-bit programmable  
count-up counters, known as Timer A and Timer B, are  
stored within two pairs of registers, TMRAL/TMRAH and  
TMRBL/TMRBH registers. Two other registers,  
RCOCCR and RCOCR control the overall operation of  
the C/R to F converter.  
Rev. 1.20  
26  
February 25, 2011  
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