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參數(shù)資料
| 型號： | MC68HC05G3 |
| 廠商： | MOTOROLA INC |
| 元件分類： | 微控制器/微處理器 |
| 英文描述： | 8-BIT, OTPROM, 2 MHz, MICROCONTROLLER, PQFP80 |
| 封裝： | QFP-80 |
| 文件頁數(shù)： | 117/128頁 |
| 文件大?。?/td> | 290K |
| 代理商： | MC68HC05G3 |
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Page 79
Section 8: TIMER SYSTEM
MOTOROLA
MC68HC05G3 (705G4) Specification Rev. 1.1
time of the read. If a read of the free-running counter or counter alternate register first
addresses the most significant byte (MSB) ($18, $1A), the LSB ($19, $1B) is transferred to
a buffer. This buffer value remains fixed after the first MSB read, even if the user reads the
MSB several times. This buffer is accessed when reading the free-running counter or
counter alternate register LSB ($19 or $1B) and, thus, completes a read sequence of the
total counter value. In reading either the free-running counter or counter alternate register,
if the MSB is read, the LSB also must be read to complete the sequence.
The counter alternate register differs from the counter register in one respect: A read of the
counter register MSB can clear the timer overflow flag (TOF). Therefore, the counter
alternate register can be read at any time without the possibility of missing timer overflow
interrupts due to clearing of the TOF.
The free-running counter is configured to $FFFC during reset and always is a read-only
register. During a power-on reset, the counter is also preset to $FFFC and begins running
after the oscillator start-up delay. Because the free-running counter is 16 bits preceded by
a fixed divided-by-four prescaler, the value in the free-running counter repeats every
262,144 internal bus clock cycles. When the counter rolls over from $FFFF to $0000, the
TOF bit is set. An interrupt also can be enabled when counter rollover occurs by setting its
interrupt enable bit (TOIE).
8.1.2
OUTPUT COMPARE REGISTER
The 16-bit output compare register is made up of two 8-bit registers at locations $16 (MSB)
and $17 (LSB). The output compare register is used for several purposes, such as
indicating when a period of time has elapsed. All bits are readable and writable and are not
altered by the timer hardware or reset. If the compare function is not needed, the two bytes
of the output compare register can be used as storage locations.
The output compare register contents are compared with the contents of the free-running
counter continually, and, if a match is found, the corresponding output compare flag (OCF)
bit is set and the corresponding output level (OLVL) bit is clocked to an output level register.
The output compare register values and the output level bit should be changed after each
successful comparison to establish a new elapsed timeout. An interrupt also can
accompany a successful output compare provided the corresponding interrupt enable bit
(OCIE) is set.
After a processor write cycle to the output compare register containing the MSB ($16), the
output compare function is inhibited until the LSB ($17) also is written. The user must write
both bytes (locations) if the MSB is written first. A write made only to the LSB ($17) will not
inhibit the compare function. The free-running counter is updated every four internal bus
clock cycles. The minimum time required to update the output compare register is a
function of the program rather than the internal hardware.
The processor can write to either byte of the output compare register without affecting the
other byte. The output level (OLVL) bit is clocked to the output level register regardless of
whether the output compare flag (OCF) is set or clear. A valid output compare must occur
before the OLVL bit becomes available at the output compare pin (TCMP) with DDRG3 set.
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PDF描述 |
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| MC68HC705J5ACJP | 8-BIT, OTPROM, 2.1 MHz, MICROCONTROLLER, PDIP16 |
| MC68HC705J5ACP | 8-BIT, OTPROM, 2.1 MHz, MICROCONTROLLER, PDIP20 |
| MC68HC05J5AJDW | 8-BIT, MROM, 2.1 MHz, MICROCONTROLLER, PDSO16 |
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相關(guān)代理商/技術(shù)參數(shù) |
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| MC68HC05J1 | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:HCMOS MICROCONTROLLER UNIT |
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| MC68HC05J1ACDW | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:Microcontrollers |
| MC68HC05J1ACP | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:Microcontrollers |
| MC68HC05J1ADW | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:Microcontrollers |
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