參數(shù)資料
型號: M68HC11D3CFB1
廠商: FREESCALE SEMICONDUCTOR INC
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 1 MHz, MICROCONTROLLER, PQFP44
封裝: QFP-44
文件頁數(shù): 60/124頁
文件大?。?/td> 5398K
代理商: M68HC11D3CFB1
OPERATING MODES AND ON-CHIP MEMORY
4-6
TECHNICAL DATA
In the second method, the MODB/VSTBY pin can supply RAM power from a battery
backup or from a second power supply, as shown in Figure 4-3. Using the MODB/
VSTBY pin may require external hardware, but can be justified when a significant
amount of external circuitry is operating from VDD. If VSTBY is used to maintain RAM
contents, reset must be held low whenever VDD is below normal operating level. Refer
Figure 4-3 RAM Standby MODB/VSTBY Connections
4.2.1 Priority and Mode Select Register
The four operating modes are selected with the logic states of the mode A (MODA)
and mode B (MODB) pins during reset. The MODA and MODB logic levels determine
the logic state of the special mode (SMOD) and mode A (MDA) control bits in the
HPRIO register.
After reset is released, the mode select pins no longer influence the MCU operating
mode. For single-chip mode, the MODA pin is connected to a logic zero. For expanded
mode, MODA is normally connected to VDD through a pull-up resistor of 4.7 k. The
MODA pin also functions as the load instruction register (LIR) pin when the MCU is not
in reset. The open drain active low LIR output pin drives low during the first E cycle of
each instruction. The MODB pin also functions as standby power input, VSTBY, which
maintains RAM contents in the absence of VDD. Refer to Table 4-2 for information
about hardware mode selection.
Table 4-2 Hardware Mode Select Summary
Inputs
Mode
Latched at Reset
MODB
MODA
RBOOT
SMOD
MDA
1
0
Single-Chip
0
1
Expanded Multiplexed
0
1
0
Special Bootstrap
1
0
1
Special Test
0
1
MODB/VSTBY CONN
4.7k
MAX
690
VBATT
+
4.8 V
NiCd
VDD
VOUT
TO MODB/VSTBY
OF M68HC11
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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