mc68hc908gr8vp Freescale Semiconductor, Inc, mc68hc908gr8vp Datasheet - Page 148

• Manufacturer Part Number: mc68hc908gr8vp
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output Ports (I/O)
PTAPUE3–PTAPUE0 — Port A Input Pullup Enable Bits
16.3 Port B
Port B is a 6-bit special-function port that shares all six of its pins with the analog-to-digital converter
(ADC) module.
16.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the six port pins.
PTB5–PTB0 — Port B Data Bits
AD5–AD0 — Analog-to-Digital Input Bits
148
These writeable bits are software programmable to enable pullup devices on an input port bit.
These read/write bits are software-programmable. Data direction of each port B pin is under the control
of the corresponding bit in data direction register B. Reset has no effect on port B data.
AD5–AD0 are pins used for the input channels to the analog-to-digital converter module. The channel
select bits in the ADC status and control register define which port B pin will be used as an ADC input
and overrides any control from the port I/O logic by forcing that pin as the input to the analog circuitry.
1 = Corresponding port A pin configured to have internal pullup
0 = Corresponding port A pin has internal pullup disconnected
Alternative Function:
Address:
Care must be taken when reading port B while applying analog voltages to
AD5–AD0 pins. If the appropriate ADC channel is not enabled, excessive
current drain may occur if analog voltages are applied to the PTBx/ADx pin,
while PTB is read as a digital input. Those ports not selected as analog
input channels are considered digital I/O ports.
PTB4 and 5 are not available in a 28-pin DIP and SOIC package
Reset:
Read:
Write:
Address:
Reset:
Read:
Write:
Figure 16-5. Port A Input Pullup Enable Register (PTAPUE)
$000D
Bit 7
0
0
$0001
Bit 7
0
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
= Unimplemented
Figure 16-6. Port B Data Register (PTB)
= Unimplemented
6
0
0
0
6
5
0
0
PTB5
AD5
5
NOTE
4
0
0
Unaffected by reset
PTB4
AD4
4
PTAPUE3
3
0
PTB3
AD3
3
PTAPUE2
2
0
PTB2
AD2
2
PTAPUE1
1
0
PTB1
AD1
1
Freescale Semiconductor
PTAPUE0
Bit 0
0
PTB0
Bit 0
AD0