MC68HC908GR8 Datasheet, PDF (59/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

I/O Registers
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is
cleared when the data register is read or the status/control register is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When this bit is set, the ADC will convert samples continuously and update the ADR register at the end
of each conversion. Only one conversion is allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH4–ADCH0 — ADC Channel Select Bits
ADCH4–ADCH0 form a 5-bit field which is used to select one of 16 ADC channels. Only six channels,
AD5–AD0, are available on this MCU. The channels are detailed in Table 5-1. Care should be taken
when using a port pin as both an analog and digital input simultaneously to prevent switching noise
from corrupting the analog signal. See Table 5-1.
The ADC subsystem is turned off when the channel select bits are all set to 1. This feature allows for
reduced power consumption for the MCU when the ADC is not being used.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
The voltage levels supplied from internal reference nodes, as specified in Table 5-1, are used to verify the
operation of the ADC converter both in production test and for user applications.
Table 5-1. Mux Channel Select
ADCH4 ADCH3 ADCH2 ADCH1 ADCH0
Input Select
0
0
0
0
0
PTB0/ATD0
0
0
0
0
1
PTB1/ATD1
0
0
0
1
0
PTB2/ATD2
0
0
0
1
1
PTB3/ATD3
0
0
1
0
0
PTB4/ATD4
0
0
1
0
1
PTB5/ATD5
0
0
1
1
0
Reserved
0
0
1
1
1
Reserved
↓
↓
↓
↓
↓
Reserved
1
1
0
1
1
Reserved
1
1
1
0
0
Reserved
1
1
1
0
1
V_REFH
1
1
1
1
0
V_REFL
1
1
1
1
1
ADC power off
NOTE: If an unknown channel is selected it should be made clear what value the user will read
from the ADC Data Register, unknown or reserved is not specific enough.
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
Freescale Semiconductor
59