
MFC2000 Multifunctional Peripheral Controller 2000
Hardware Description
24-8
Conexant
100723A
24.3 ARM BUS INTERFACE
24.3.1 Function Description
The Arm Bus interface block attaches the Countach Bus Subsystem to the ARM Bus System. The ARM can
directly access the various registers of the Countach Bus Subsystem. It can access the Countach Bus
Subsystem’s SDRAM and the Countach Imaging DSP subsystem’s scratch pad memory and the SDRAM with
discrete I/O accesses with some wait state penalty. It can also access the SDRAM via DMA accesses. To
accommodate the ARM DMA interchange, two channels are provided: one for transfers into the SDRAM and one
for transfers out of the SDRAM.
In addition, two handshaking signals are provided for interrupting of each processor and allow the ARM to
interrupt the Countach core. It is implemented through a register in the Countach Subsystem Interface. The
arm_attn signal comes directly from the Countach core and is an input to the ARM interrupt controller.
24.3.2 Register Description
Address:
ARM Bus Interface
Interrupt Status
(ABIIrqStat)
$01FF8283
Address:
ARM Bus Interface
Interrupt Status
Bit 15
(Not Used)
Bit 14
(Not Used)
Bit 13
(Not Used)
Bit 12
(Not Used)
Bit 11
(Not Used)
Bit 10
(Not Used)
Bit 9
(Not Used)
Bit 8
(Not Used)
Default:
Rst. Value
xxh
Read Value
00h
Bit 7
(Not Used)
Bit 6
(Not Used)
Bit 5
Countach
Subsystem
Interrupt
Bit 4
VSI
Overrrun
Bit 3
Deferred
Access
Done
Bit 2
C2A DMA
Done
Bit 1
Countach
DMA Done
Bit 0
Video/
Default:
Rst Value
(ABIIrqStat)
$01FF8282
Scan DMA
Done
xx000000b
Read Value
00h
Bit 15-6
Bit 5
Not used
Countach Subsystem has interrupted the ARM either in IRQP or
IRQP2, depending on the setting of the Countach Interrupt Source bit
of the ABICountachCtrl register.
The second VSI ping-pong buffer has been filled before the first has
been emptied, resulting in loss of data.
A deferred access to/from scratch pad or SDRAM has completed. If a
deferred read was requested, the data in the Deferred Read Access
Data register is now valid.
C2A (SDRAM to Arm Bus System) block size has been reached.
DMA operation specified by Countach scratch pad parameters has
completed.
Two-dimensional DMA from Video/Scan Interface to SDRAM has
completed (two fields) or one scan line has completed.
Countach Subsystem Interrupt
Bit 4
VSI Overrun
Bit 3
Deferred Access Done
Bit 2
Bit 1
C2A DMA Done
Countach DMA Done
Bit 0
Video/Scan DMA Done
Note
: Each of these bits are cleared by writing it to a one. This allows individual interrupts to be
cleared without affecting the others.