MC9S08JM16 Datasheet, PDF (80/386 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 6 Parallel Input/Output
6.5 Parallel I/O and Pin Control Registers
This section provides information about the registers associated with the parallel I/O ports and pin control
functions. These parallel I/O registers are located in page zero of the memory map and the pin control
registers are located in the high page register section of memory.
Refer to tables in Chapter 4, “Memory,” for the absolute address assignments for all parallel I/O and pin
control registers. This section refers to registers and control bits only by their names. A Freescale-provided
equate or header file normally is used to translate these names into the appropriate absolute addresses.
6.5.1 Port A I/O Registers (PTAD and PTADD)
Port A parallel I/O function is controlled by the registers listed below.
7
R
W
Reset
0
6
5
4
3
2
PTAD5
0
0
0
0
0
Figure 6-2. Port A Data Register (PTAD)
1
0
PTAD0
0
0
Table 6-1. PTAD Register Field Descriptions
Field
Description
5,0
PTAD[5,0]
Port A Data Register Bits — For port A pins that are inputs, reads return the logic level on the pin. For port A
pins that are configured as outputs, reads return the last value written to this register.
Writes are latched into all bits of this register. For port A pins that are configured as outputs, the logic level is
driven out the corresponding MCU pin.
Reset forces PTAD to all 0s, but these 0s are not driven out the corresponding pins because reset also configures
all port pins as high-impedance inputs with pullups disabled.
7
R
W
Reset
0
6
5
4
3
2
1
PTADD5
0
0
0
0
0
0
Figure 6-3. Data Direction for Port A Register (PTADD)
0
PTADD0
0
Table 6-2. PTADD Register Field Descriptions
Field
Description
5,0
PTADD[5,0]
Data Direction for Port A Bits — These read/write bits control the direction of port A pins and what is read for
PTAD reads.
0 Input (output driver disabled) and reads return the pin value.
1 Output driver enabled for port A bit n and PTAD reads return the contents of PTADn.
MC9S08JM16 Series Data Sheet, Rev. 2
80
Freescale Semiconductor