Freescale Semiconductor HCS08 Series, Reference Manual

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Chapter 6 Parallel Input/Output
MC9S08JS16 MCU Series Reference Manual, Rev. 4
82 Freescale Semiconductor
Refer to tables in Chapter 4, “Memory ,” for the absolute address assignments of 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.
6.5.2 Port A Pin Control Registers (PTAPE, PTASE, PTADS)
In addition to the I/O control, port A pins are controlled by the registers listed below.
7 6 5 4 3 2 1 0
R
PTAD7 PTAD6 PTAD5 PTAD4 PTAD3 PTAD2 PTAD1 PTAD0
W
Reset 0 0 0 0 0 0 0 0
Figure 6-2. Port A Data Register (PTAD)
Table 6-1. PTAD Register Field Descriptions
Field Description
7:0
PTAD[7:0]
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 6 5 4 3 2 1 0
R
PTADD7 PTADD6 PTADD5 PTADD4 PTADD3 PTADD2 PTADD1 PTADD0
W
Reset 0 0 0 0 0 0 0 0
Figure 6-3. Data Direction for Port A Register (PTADD)
Table 6-2. PTADD Register Field Descriptions
Field Description
7:0
PTADD[7:0]
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.