Programmable Input/Output
23-4 Élan™SC520 Microcontroller User’s Manual
23.4 REGISTERS
A summary listing of the memory-mapped configuration registers used to control the PIO
signals is shown in Table 23-2.
23.5 OPERATION
All PIO signal pins can be programmed as inputs, outputs, or to support their interface
function (e.g., GP bus signals). They are enabled as PIO inputs at power-on reset, with
built-in pullup or pulldown resistors.
As inputs, PIOs are used by software to monitor signals from other devices. They provide
a path to bring signals into the chip that are not available through the other interfaces.
As outputs, the PIOs provide the ability for software to control external devices with signals
that can be driven High or Low.
Table 23-2 PIO Registers—Memory-Mapped
Register Mnemonic
MMCR
Offset
Address Function
PIO15–PIO0 Pin Function
Select
PIOPFS15_0 C20h PIO15–PIO0 or interface function select:
GPIRQ10–GPIRQ8, GPDACK3
–GPDACK0,
GPDRQ3–GPDRQ3, GPTC, GPAEN, GPRDY,
GPBHE
, GPALE
PIO31–PIO16 Pin Function
Select
PIOPFS31_16 C22h PIO31–PIO16 or interface function select: RIN2
,
DCD2
, DSR2, CTS2, GPCS0, GPMEMCS16,
GPIOCS16
, GPDBUFOE, GPIRQ7–GPIRQ0
Chip Select Pin Function
Select
CSPFS C24h GPCS7
–GPCS1 or alternate function select:
TMROUTx, TMRINx, PITGATE2, ROMCS2
,
ROMCS1
Clock Select CLKSEL C26h CLKTIMER[CLKTEST] pin enable, clock output
select options (18.432 MHz or 1.8432 MHz
UART, PLL1, PLL2, PIT, and RTC), CLKTIMER
or CLKTEST select
Drive Strength Control DSCTL C28h I/O pad drive strength for SCS3
–SCS0,
SRASA
–SRASB, SCASA–SCASB, SWEA–
SWEB
, SDQM3–SDQM0, MA12–MA0, MD31–
MD0, MECC6–MECC0.
PIO15–PIO0 Direction PIODIR15_0 C2Ah PIO15–PIO0 as input or output
PIO31–PIO16 Direction PIODIR31_16 C2Ch PIO31–PIO16 as input or output
PIO15–PIO0 Data PIODATA15_0 C30h Read/write directly the state of the PIO15–PIO0
pin
PIO31–PIO16 Data PIODATA31_16 C32h Read/write directly the state of the PIO31–
PIO16 pin
PIO15–PIO0 Set PIOSET15_0 C34h Drive PIO15–PIO0 output High
PIO31–PIO16 Set PIOSET31_16 C36h Drive PIO31–PIO16 output High
PIO15–PIO0 Clear PIOCLR15_0 C38h Drive PIO15–PIO0 output Low
PIO31–PIO16 Clear PIOCLR31_16 C3Ah Drive PIO31–PIO16 output Low
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