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8.7.3 General-Purpose I/O Pins
When a microprocessor interface is enabled (
IFSEL≠ 000), there are two general-purpose I/O (GPIO) pins
available per port, each of which can be used as a general-purpose input, general-purpose output, or loss-of-signal
output. In addition, GPIOB1, GPIOB2, and GPIOB3 can be used as a global I/O signal. The GPIO pins are
GLOBAL.GIOBRR registers. When a GPIO pins is configured as a loss-of-signal status output, its state mimics the
state of the
LINE.RSR:LOS status bit. When a port is powered down and a GPIO pin has been programmed as an
associated loss-of-signal output, the pin is held low. Programming a GPIO pin as a global signal overrides the I/O
settings specified by the GPIOynS field for that pin and configures the pin as an input or an output as shown in
Table 8-14. GPIO Pin Global Signal Assignments
GLOBAL SIGNAL
PIN
FUNCTION
CONTROL BIT
GPIOAn
None
—
GPIOB1
Global PMU input
GPIOB2
Global TMEI input
GPIOB3
1SREF output
GPIOBk
None
—
Note:
n = 1 to 12, k = 4 to 12.
Table 8-15. GPIO Pin Control
GPIOynS[1:0]
FUNCTION
00
Input
01
Output LOS status for port n
10
Output logic 0
11
Output logic 1
Note:
n = 1 to 12, y = A or B.
8.7.4 Performance Monitor Register Update
Each performance monitor counter can count at least one second of events before saturating at the maximum
count. Each counter has an associated status bit that is set when the counter value is not zero, a latched status bit
that is set when the counter value changes from zero to one, and a latched status bit that is set each time the
counter is incremented.
There is a holding register for each performance monitor counter that is updated when a performance monitoring
update is performed. A performance monitoring update causes the counter value to be loaded into the holding
register and the counter to be cleared. If a counter increment occurs at the exact same time as the counter reset,
the counter is loaded with a value of one, and the “counter is non-zero” latched status bit is set.
The performance monitor update (PMU) signal initiates a performance monitoring update. The PMU signal can be
sourced from a general-purpose I/O pin (GPIOB1), the internal one-second reference, a global register bit
PORT.CR1:PMUM bits are set to 1, and the appropriate
BERT.CR:PMUM bits are set to 1. To use the internal one-
second reference,
GLOBAL.CR1:GPM[1:0] is set to 1X, the appropriate
PORT.CR1:PMUM bits are set to 1, and
set to 00, the appropriate
PORT.CR1:PMUM bits are set to 1, and the appropriate
BERT.CR:PMUM bits are set to
1. To use the port PMU register bit, the associated
PORT.CR1:PMUM bit is set to 0, and the appropriate
set to 0.
When using the global or port PMU register bits, the PMU bit should be set to initiate the process and cleared when
one-second reference, the PMS bit is set shortly after the signal goes high, and cleared shortly after the signal