參數(shù)資料
型號: MC68HC11A8BVP2
廠商: MOTOROLA INC
元件分類: 微控制器/微處理器
英文描述: HCMOS Single-Chip Microcontroller
中文描述: 8-BIT, MROM, 2 MHz, MICROCONTROLLER, PDIP48
封裝: DIP-48
文件頁數(shù): 20/158頁
文件大?。?/td> 776K
代理商: MC68HC11A8BVP2
MOTOROLA
2-4
SIGNAL DESCRIPTIONS AND OPERATING MODES
MC68HC11A8
TECHNICAL DATA
2
2.1.8 A/D Converter Reference Voltages (V
RL
, V
RH
)
These two inputs provide the reference voltages for the analog-to-digital converter cir-
cuitry.
2.1.9 Strobe B and Read/Write (STRB/R/W)
This signal acts as a strobe B output or as a data bus direction indicator depending on
the operating mode.
In single-chip operating mode, the STRB output acts as a programmable strobe for
handshake with other parallel l/O devices. Refer to
4 PARALLEL I/O
for additional in-
formation.
In expanded multiplexed operating mode, R/W is used to control the direction of trans-
fers on the external data bus. A low on the R/W signal indicates data is being written
to the external data bus. A high on this signal indicates that a read cycle is in progress.
R/W will stay low during consecutive data bus write cycles, such as in a double-byte
store. The NAND of inverted R/W with the E clock should be used as the write enable
signal for an external static RAM.
2.1.10 Strobe A and Address Strobe (STRA/AS)
This signal acts as an edge detecting strobe A input or as an address strobe bus con-
trol output depending on the operating mode.
In single-chip operating mode, the STRA input acts as a programmable strobe for
handshake with other parallel l/O devices. Refer to
4 PARALLEL I/O
for additional in-
formation.
In expanded multiplexed operating mode, the AS output is used to demultiplex the ad-
dress and data signals at port C. Refer to
2.2.2 Expanded Multiplexed Operating
Mode
for additional information.
2.1.11 Port Signals
Ports A, D, and E signals are independent of the operating mode. Port B provides eight
general purpose output signals in single-chip operating modes and provides eight
high-order address signals when the microcontroller is in expanded multiplexed oper-
ating modes. Port C provides eight general purpose input/output signals when the mi-
crocontroller is in singlechip operating modes. When the microcontroller is in
expanded multiplexed operating modes, port C is used for a multiplexed address/data
bus.
Table 2-2
shows a summary of the 40 port signals as they relate to the operating
modes. Unused inputs and l/O pins configured as inputs should be terminated high or
low.
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