CS4281 Programming Manual
DS308PRM1
79
Confidential Draft
3/7/00
Count, TC, or Half the Terminal Count, HTC.
HISR indicates which DMA is causing the inter-
rupt. The interrupts are enabled through the upper
word in the DCRn register. The interrupt condition
is cleared by reading the Host DMA Status Regis-
ter, HDSRn, which also indicates which interrupt
occurred (TC or HTC). DMA interrupt conceptual
logic is illustrated in Figure 21.
When in Polled FIFO mode (attached
DMAn.POLL
= 1), the DMAn engine supports the
transfer of data between the host software (FPDRn)
and FIFOn. Interrupts are enabled through the up-
per word of FSICn. HISR indicates which FIFO is
causing the interrupt. Interrupts are cleared by
reading the lower word of the FSICn register,
which also indicates which type of FIFO interrupt
occurred. As an example, HISR indicates that
FIFO0 caused an interrupt, then the interrupt status
and clearing occurs in FSIC0. The FIFO interrupt
conceptual logic is illustrated in Figure 22.
10.3
Extended GPIO and Hardware
Volume Control Interrupts
The extended GPIO pins can be configured
through the GPIOR register to cause interrupts.
Four pins have this capability:
GPIO3
,
ASDIN2/GPIO1
,
VOLUP
,
VOLDN
. All GPIO
interrupts are cleared by writing a 0 to the
appropriate status bit in GPIOR. To configure for
interrupts,
GPIO3
and
ASDIN2/GPIO1
must have
the following:
•
Configured as an input (
GPIOR.GPxOE
= 0,
where x is 1 or 3)
•
Configured as sticky (
GPIOR.GPxST
= 1)
•
Interrupt mask bit cleared (
HICR.GPxIM
=
0)
The
ASDIN2/GPIO1
pin must also NOT be config-
ured for
ASDIN2
. Conceptual logic for GPIO pins as
well as hardware volume control pins is illustrated
in the General Purpose Input/Output Pins section:
Figures 49 through 51.
The
VOLUP/VOLDN
pins are always inputs and can
generate interrupts either as general purpose inputs
or while being used as hardware volume control.
For these pins to generate interrupts, the following
configuration is used:
•
Configured as sticky (
GPIOR.VxxST
= 1,
where xx is UP and DN for the two pins)
•
Individual mask bit cleared (
HICR.VxxIM
=
0)
When hardware volume is enabled
(
SSCR.HVC
= 1), the GPIO logic can be triggered
every time the hardware volume is updated (
GPI-
OR.VxxLT
= 1). This feature enables host software
to keep track of master volume changes, or allows
host software to totally control the master volume
updates.
D
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ft
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