Agere Systems Inc.
101
Data Sheet
May 2001
and Packet Payload Engine
Ambassador T8110 PCI-Based H.100/H.110 Switch
9 General-Purpose I/O
(continued)
9.2.1 GPIO General-Purpose Bits
Any of the T8110 GP signals may be used as general-purpose I/O bits. Each GP bit used as GPIO is configured by
setting the direction via the appropriate bits in the GPIO R/W register. For write access to the GPIO, the GPIO data
register is used to hold data for output to the GP pin(s). Read accesses are maskable via the GPIO read mask reg-
ister. For read access from the GPIO, the logical state of the GP[7:0] signals is returned if unmasked. If a GPIO bit
is masked, a read access returns 0.
9.2.2 GP Dual-Purpose Bits GPIO (Override)
9.2.2.1 GP H.110 Clock Master Indicators (GP0, GP1 Only)
An additional function is provided for GP0 and GP1 only, controlled via the GPIO override register.
GP0 may be used as a dedicated output (set GPIO override register bit 0), which transmits the state of the T8110
A clock master enable (register 0x00220, bit 4). This output is intended to drive the external A clock FETs required
for H.110 bus mastering.
GP1 may be used as a dedicated output (set GPIO override register bit 1), which transmits the state of the T8110
B clock master enable (register 0x00220, bit 5). This output is intended to drive the external B clock FETs required
for H.110 bus mastering.
9.2.2.2 PCI_RST# Indicator (GP2 Only)
An additional function is provided for GP2 only, controlled via the GPIO override register. GP2 may be used as a
dedicated output (set GPIO override register bit 2), which forwards the state of the PCI_RST# signal. Polarity of
the transmitted signal is selectable via register 0x00780 (refer to Section 11.2 on page 110). This function provides
access to a forwarded PCI_RST# signal by external devices hanging off the minibridge port.
9.2.3 GP External Interrupts
Any of the T8110 GP signals may be used as externally sourced inputs into the interrupt controller logic. Each GP
bit used as an interrupt input must be shut off by setting the appropriate GPIO R/W register bit to be input. The
interrupt control register
s (0x00604—607) control how the GP inputs are handled. For more details, see Section
12.1 on page 113.
9.2.4 GP Diagnostic Test Point Observation
Any of the T8110 GP signals may be used to observe a predefined set of internal test-points. Each GP bit used as
a test-point output is enabled via diagnostic register 0x00142, GP test-point enable. Settings in this register over-
ride the GPIO R/W register and force the selected bits to be test-point outputs (refer to Section 13.1 on page 128,
and Table 105 on page 130).