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| 型號： | MC68HC16Z1VEH16 |
| 廠商： | Freescale Semiconductor |
| 文件頁數(shù)： | 53/56頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC MCU 16BIT 1K FLASH 132-PQFP |
| 標準包裝： | 36 |
| 系列： | HC16 |
| 核心處理器： | CPU16 |
| 芯體尺寸： | 16-位 |
| 速度： | 16MHz |
| 連通性： | EBI/EMI，SCI，SPI |
| 外圍設備： | POR，PWM，WDT |
| 輸入/輸出數(shù)： | 16 |
| 程序存儲器類型： | ROMless |
| RAM 容量： | 1K x 8 |
| 電壓 - 電源 (Vcc/Vdd)： | 2.7 V ~ 5.5 V |
| 數(shù)據(jù)轉(zhuǎn)換器： | A/D 8x10b |
| 振蕩器型： | 內(nèi)部 |
| 工作溫度： | -40°C ~ 105°C |
| 封裝/外殼： | 132-BQFP 緩沖式 |
| 包裝： | 托盤 |
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MC68HC16Z1TUT/D
onboard chip-select lines.
Using 8-bit memory simplifies the design and reduces cost, but with a significant performance penalty.
This penalty is not fixed, but depends on the amount of time that the processor spends accessing the
8-bit memory as opposed to accessing other external memory or performing internal accesses or oper-
ations. Moving from 16-bit to 8-bit program memory may reduce CPU performance by 40% when exe-
cuting simple CPU instructions that only take a few clock cycles to execute. The impact is less in
systems that make intensive use of CPU registers and complex instructions.
As a general guide:
Use fast/word memory for the CPU stack, especially when programming in high level languages.
Use fast/word memory for frequently accessed variables.
Use fast/word memory for time critical routines, perhaps by copying them from slow main ROM into
fast external or internal RAM.
Use slow/byte memory for rarely executed, non-critical routines, such as initialization routines.
2.3 Pins that Need Pull-Up Resistors
Many of the input pins need pull-up resistors to prevent unexpected conditions. The pins discussed be-
low must be conditioned in all applications. An incorrect voltage on one or more of them can cause gen-
eral system failure. Other input pins, such as TPU inputs, can be left floating without adverse effect in
certain applications. The designer must determine which pins can cause system failure in a particular
application and deal with them appropriately. In general, it is best to condition all input pins so that they
are in a known state, whether they are used or not.
Never connect a pin directly to 5 volts if it is possible to configure the pin as an output. Attempting to
drive an output low when it is connected to voltage source can damage the output drivers. Many of the
pins have dual functions and can be configured as I/O pins by holding specific data bus lines low during
reset. When a pin is configured for I/O during reset and will never be reconfigured for the alternate func-
tion, a pull-up resistor may not be needed. Table 1 shows which signals are affected by data bus pin
state during reset.
BR/CS0 — Use a 10 K
pull-up to prevent an unexpected bus request. This pin is configured as a chip-
select pin when DATA1 is held high at the release of reset. Conditioning DATA1 as described in 2.1
Using Data Bus Pins to Configure the MCU precludes use of a pull-up.
BERR — This is an input signal that is asserted in the absence of DSACK to indicate a bus error con-
dition. Using a 10 K
pull-up resistor prevents the unexpected assertion of bus error.
HALT — This is an active-low bidirectional signal that can be used to halt the external bus, among other
things. Using a 10 K
pull-up resistor will prevent an erroneous bus halt. Since HALT is a bidirectional
signal, do not connect it directly to BERR, RESET or 5 Volts.
IRQ[7:1] — Although the interrupt lines have internal pull-up circuitry, the circuitry is weak and can be
overcome by noise and capacitive coupling. Make certain that pins configured for use as interrupt-re-
quest inputs rather than for use as general-purpose I/O are pulled up to 5 Volts.
There are two ways to lessen the chances for erroneous interrupt service requests:
1. Hold DATA9 low during reset as described in 2.1 Using Data Bus Pins to Configure the MCU
to assign all these pins to general-purpose I/O port F. Pull up lines that are to be used for interrupt
service to 5 V via 10 K
resistors, hold DATA9 low during reset, reassign the pins to be used for
interrupt requests by writing to the port F pin assignment register, then change the IPL mask val-
ue to enable maskable interrupts.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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