TransDimension Inc.
Interfacing TD242LP to Intel StrongArm SA1110 Processor
The SA1110’s GPIO control registers should be initialized as follows:
Register
GPDR
GFER
Register Full Name
GPIO Pin Direction Register
GPIO Falling-Edge Detect Register
GPIO Alternate Function Register
Bit 14
Meaning
input
enable
gpio
Default
0
1
0
0
undefined
0
GAFR
Figure 16: SA1110 GPIO register settings to support TD242LP interrupt
To enable interrupt, the SA1110 interrupt control registers should be set as follows:
Register
ICLR
ICMR
Register Full Name
Interrupt Controller Level Register
Interrupt Controller Mask Register
Bit 14
Meaning
IRQ
Enable
Default
undefined
undefined
0
1
Figure 17: SA1110 interrupt control register settings to support TD242LP interrupt
In addition, if the user application requires the SA1110 be brought out of the idle mode upon an
interrupt from the TD242LP, Bit 0 of the SA1110 register ICCR (Interrupt Controller Control
Register) should be set accordingly.
Please note that the interrupt generated by the TD242LP is level sensitive. Caution must be taken
when it is interfaced with an interrupt controller, such as the one in the SA1110, that supports
only edge-sensitive interrupt sources. In this case, a one more check of interrupt status register
may be necessary right before getting out of the ISR (the Interrupt Service Routine), which will
prevent from missing any interrupt.
Interrupt: TD242LP Configuration
The software must configure the TD242LP before the SA1110 enables the interrupt originated
from it. The following steps must be carried out:
Step 1: Configure the TD242LP INT pin to be active low. This requires Bit 16 of the TD242LP
Hardware Mode Register (000H) be set to 0, which is the default.
Step 2: Configure the TD242LP INT pin to be totem-pole output. This requires Bit 21 of the
IOConfiguration2 Register (04CH) to be set to 1 by user software. Note that the INT pin
defaults to wired OR output, which should also work if a pull-up resistor is present.
Step 3: Enable interrupt sources on the TD242LP side, which involves four sets of registers as
described in detail in Section 4 of the TD242LP Technical Manual.
USB System Initialization
It should be emphasized that all SA1110 register settings and the TD242LP hardware system
settings discussed above must be completed before the USB controllers within the TD242LP are
activated.
TransDimension, Inc.
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