SA1110 Datasheet, PDF (75/406 Pages) Intel Corporation – Intel StrongARM SA-1110 Microprocessor

System Control Module
9.1.1.3
GPIO Pin Output Set Register (GPSR) and Pin Output Clear Register
(GPCR)
When a port is configured as an output, the user controls the state of the pin by writing to either the
GPIO pin output set register (GPSR) or the GPIO pin output clear register (GPCR). An output pin
is set by writing a one to its corresponding bit within the GPSR. To clear an output pin, a one is
written to the corresponding bit within the GPCR. These are write-only registers. Reads return
unpredictable values. Writing a zero to any of the GPSR or GPCR bits has no effect. Writing a one
to a GPSR or GPCR bit corresponding to a pin that is configured as an input has no effect. For
reserved bits, writes are ignored. The following tables show the locations of the GPSR bits and the
locations of the GPCR bits. These are write-only registers and reset values do not apply.
0h 9004 0008
GPSR
Write-Only
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
Bits
n
31..28
Name
PSn
—
Description
GPIO output pin set n (where n = 0 through 27).
0 – Pin level unaffected.
1 – If pin configured as an output, set pin level high (one).
Reserved
0h 9004 000C
GPCR
Write-Only
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
Bits
n
31..28
Name
PCn
—
Description
GPIO output pin clear n (where n = 0 through 27).
0 – Pin level unaffected.
1 – If pin configured as an output, clear pin level low (zero).
Reserved
The user can test a bit within the GPLR corresponding to a pin that is configured as an output after
having set or cleared the pin state to determine if there is an external conflict on the pin. For
example, if an off-chip device is driving a GPIO output pin high and the user has cleared the pin’s
state by writing a one to its GPCR bit, the user can read the GPLR, then compare the written value
(zero) to the actual value (one) to detect the conflict.
SA-1110 Developer’s Manual
9-5