
7.0 General-Purpose Input/Output (GPIO) Ports
(Continued)
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P
System notification through IRQ, SMI or SCI (see Section 9.2.1 on page 162) can be initiated by software by writing to the
Data Out bit (in the GPDO register) of a GPIO pin. This is possible only if the output of the corresponding GPIO pin is en-
abled, pin multiplexing is selected for the GPIO function (see Section 1.3 on page 20) and the GPIO event is routed to IRQ,
SMI or SCI. System notification is asserted according to the actual level at the GPIO pin driven by the GPIO output and/or
by external circuitry. The level driven by the GPIO output should not cause a contention with the level driven by the external
circuitry.
A pending edge event may be cleared by clearing the corresponding GPEVST bit. However, a level event source may not
be released by software (except for disabling the source) as long as the pin is at active level. When level event is used, it is
also recommended to disable the input debouncer.
Upon deactivation of the GPIO functional block and while the V
DD
power is Off, access through the LPC bus to the runtime
registers (GPEVST and GPEVEN) is disabled. All means of system notification that include the target IRQ number are de-
tached from the GPIO and de-asserted.
When the V
DD
power is Off, the status bits of the GPIO pins connected to a V
DD
-powered device (VDDLOAD = 1) are cleared,
however the status bits of the GPIO pins connected to a V
SB
-powered device (VDDLOAD = 0) is not affected.
Before enabling any system notification, it is recommended to set the desired event configuration and then verify that the
status registers are cleared.
7.4
The following abbreviations are used to indicate the Register Type:
GPIO PORT REGISTERS
G
R/W
= Read/Write.
G
R
= Read from a specific register (write to the same address is to a different register).
G
W
= Write (see above).
G
RO
= Read Only.
G
WO
= Write Only. Reading from the bit returns 0.
G
R/W1C= Read/Write 1 to Clear. Writing 1 to a bit clears it to 0. Writing 0 has no effect.
G
R/W1S = Read/Write 1 to Set. Writing 1 to a bit sets its value to 1. Writing 0 has no effect.
7.4.1
For each Port, there is a group of eight identical sets of configuration registers. Each set is associated with one GPIO pin.
The entire group is mapped to the PnP configuration space. The mapping scheme is based on the GPSEL register (see
Section 3.14.3 on page 72), which functions as an index register, and the specific GPCFG1, GPEVR and GPCFG2 registers
that reflect the configuration of the currently selected pin (see Table 34). All these registers are V
SB
powered.
GPIO Pin Configuration Registers Structure
Table 34. GPIO Configuration Registers
Index
Configuration Register or Action
Type
Power Well
Reset
F0h
GPIO Pin Select register (GPSEL).
R/W
V
SB
00h
F1h
GPIO Pin Configuration register 1 (GPCFG1).
R/W
V
SB
Note
1
1. See Section 3.14.3 on page 72.
F2h
GPIO Pin Event Routing register (GPEVR).
R/W
V
SB
01h
F3h
GPIO Pin Configuration register 2 (GPCFG2).
R/W
V
SB
00h