Programmable I/O Signals
Am186™CC/CH/CU Microcontrollers User’s Manual
9-7
9.5.6
Hardware-Related Considerations
Choose your PIOs wisely. The following PIO signals are multiplexed with alternate signals
that may be used by emulators: PIO8, PIO15, PIO33, PIO34, and PIO35. Consider any
emulator requirements for the alternate signals before using these pins as PIOs. For more
information, see Chapter 4, “Emulator Support.”
9.5.7
Software-Related Considerations
■
The PIO Set and PIO Clear registers provide an efficient, nondestructive means to modify
specific data values for the PIOs. Previous Am186 devices required the user to perform
a read-mask-modify-write approach when modifying PIO data values (and preserving
the values of other bits in the register). With the PIO Set and PIO Clear registers, specific
bits can be set or cleared in a single write.
■
When configuring PIOs, modify only the bits relevant to your application by reading the
existing register value, masking the bits needed, and writing the register.
9.5.8
Comparison to Other Devices
■
The PIO registers are similar to previous Am186 controller implementations. The PIO
Mode, PIO Direction, and PIO Data registers behave similarly; the PIO Set and PIO
Clear registers have been added.
■
The Am186CC/CH/CU microcontrollers offer 48 PIOs rather than the 32 offered in other
Am186 implementations, and these PIOs have different pin assignments.
9.6
INITIALIZATION
On both an external and internal reset, the following occurs:
■
The PIOMODE0 register defaults to 0000h, the PIODIR0 register to 1EFFh, PIOMODE1
to 0000h, PIODIR1 to 9FFFh, PIOMODE2 to 0000h, and PIODIR2 to FFF1h. This
defaults the PIOs to various configurations as shown in Table 9-1 on page 9-3. (PIO8,
PIO13, PIO14, PIO15, PIO29, PIO30, PIO33, PIO34, and PIO35 default to their alternate
operation. The remaining PIOs default to the PIO function.) System initialization code
must reconfigure PIOs as required.
■
The PIOSETx and PIOCLRx registers default to 0000h.
■
The PIODATAx registers default to values dependent on the system configuration. For
more information, see the
Am186™CC/CH/CU Microcontrollers Register Set Manual,
order #21916.
Summary of Contents for Am186 CC
Page 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Page 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Page 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Page 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Page 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Page 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Page 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Page 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Page 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...