MC68HC912BL16 Datasheet, PDF (10/128 Pages) Freescale Semiconductor, Inc – 16-Bit Microcontroller

Freescale Semiconductor, Inc.
3.2 Power Supply Pins
MC68HC912BL16 power and ground pins are described below and summarized in Table 4.
3.2.1 Internal Power (V_DD) and Ground (V_SS)
Power is supplied to the MCU through V_DD and V_SS. Because fast signal transitions place high, short-
duration current demands on the power supply, use bypass capacitors with high-frequency character-
istics and place them as close to the MCU as possible. Bypass requirements depend on how heavily
the MCU pins are loaded.
3.2.2 External Power (V_DDX) and Ground (V_SSX)
External power and ground for I/O drivers. Because fast signal transitions place high, short-duration cur-
rent demands on the power supply, use bypass capacitors with high-frequency characteristics and
place them as close to the MCU as possible. Bypass requirements depend on how heavily the MCU
pins are loaded.
3.2.3 V_DDA, V_SSA
Provides operating voltage and ground for the analog-to-digital converter. This allows the supply volt-
age to the A/D to be bypassed independently.
3.2.4 Analog-to-Digital Reference Voltages (V_RH, V_RL)
3.2.5 V_FP
Flash EEPROM programming voltage and supply voltage during normal operation.
Table 4 MC68HC912BL16 Power and Ground Connection Summary
Mnemonic
V_DD
V_SS
V_DDX
V_SSX
V_DDA
V_SSA
V_RH
V_RL
V_FP
Pin Number
Description
38
Internal power and ground.
39
22, 60
21, 59
External power and ground, supply to pin drivers.
50
Operating voltage and ground for the analog-to-digital converter,
51
allows the supply voltage to the A/D to be bypassed independently.
40
Reference voltages for the analog-to-digital converter.
41
58
Programming voltage for the Flash EEPROM and required supply
for normal operation.
3.3 Signal Descriptions
3.3.1 Crystal Driver and External Clock Input (XTAL, EXTAL)
These pins provide the interface for either a crystal or a CMOS compatible clock to control the internal
clock generator circuitry. Out of reset the frequency applied to EXTAL is twice the desired E-clock rate.
All the device clocks are derived from the EXTAL input frequency.
MC68HC912BL16
10
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