參數(shù)資料
型號: MC68HC11D3VFN
廠商: 飛思卡爾半導(dǎo)體(中國)有限公司
英文描述: ROM-based high-performance microcontrollers
中文描述: 基于ROM的高性能微控制器
文件頁數(shù): 40/124頁
文件大?。?/td> 840K
代理商: MC68HC11D3VFN
OPERATING MODES AND ON-CHIP MEMORY
For More Information On This Product,
Go to: www.freescale.com
4-6
TECHNICAL DATA
In the second method, the MODB/V
STBY
pin can supply RAM power from a battery
backup or from a second power supply, as shown in
Figure 4-3
. Using the MODB/
V
STBY
pin may require external hardware, but can be justified when a significant
amount of external circuitry is operating from V
DD
. If V
STBY
is used to maintain RAM
contents, reset must be held low whenever V
DD
is below normal operating level. Refer
to
SECTION 5 RESETS AND INTERRUPTS
.
Figure 4-3 RAM Standby MODB/V
STBY
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 V
DD
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, V
STBY,
which
maintains RAM contents in the absence of V
DD
. Refer to
Table 4-2
for information
about hardware mode selection.
Table 4-2 Hardware Mode Select Summary
Inputs
Mode
Latched at Reset
SMOD
0
0
1
1
MODB
1
1
0
0
MODA
0
1
0
1
RBOOT
0
0
1
0
MDA
0
1
0
1
Single-Chip
Expanded Multiplexed
Special Bootstrap
Special Test
MODB/VSTBY CONN
4.7k
MAX
690
V
BATT
+
4.8 V
NiCd
V
DD
V
DD
V
OUT
TO MODB/V
STBY
OF M68HC11
F
Freescale Semiconductor, Inc.
n
.
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