s5935qrc Applied Micro Circuits Corporation (AMCC), s5935qrc Datasheet - Page 80

• Manufacturer Part Number: s5935qrc
• Description: Pci Product
• Manufacturer: Applied Micro Circuits Corporation (AMCC)

S5935 – PCI Product
ADD-ON CONTROLLED BUS MASTER
READ ADDRESS REGISTER (MRAR)
This register is only accessible when Add-On initiated
bus mastering is enabled.
This register is used to establish the PCI address for
data moving to the Add-On bus from the PCI bus dur-
ing PCI bus memory read operations. It consists of a
30-bit counter with the low-order two bits hardwired as
zeros. Transfers may be any non-zero byte length as
defined by the transfer count register, MRTC and must
begin on a DWORD boundary. This DWORD bound-
ary starting constraint is placed upon this controller’s
PCI bus master transfers so that byte lane alignment
can be maintained between the S5395X controller’s
internal FIFO data path, the Add-On interface and the
PCI bus.
Figure 33. Add-On Controlled Bus Master Read Address Register
80
Register Name
Add-On
Address Offset
Power-up value
Attribute
Size
31
DS1527
Master Read Address
30h
00000000h
Read/Write
32 bits
Note: Applications which require a non-DWORD start-
ing boundary will need to move the first few bytes
under software program control (and without using the
FIFO) to establish a DWORD boundary. After the
DWORD boundary is established the S5935 can begin
the task of PCI bus master data transfers.
The Master Read Address Register is continually
updated during the transfer process and will always be
pointing to the next unread location. Reading of this
register during a transfer process (done when the
S5935 controller is functioning as a target—i.e., not a
bus master) is permitted and may be used to monitor
the progress of the transfer. During the address phase
for bus master read transfers, the two least significant
bits presented on the PCI bus AD[31:0] will always be
zero. This identifies to the target memory that the burst
address sequence will be in a linear order rather than
in an Intel 486 or Pentium™ cache line fill sequence.
Also, the PCI bus address bit A1 will always be zero
when this controller is the bus master. This signifies to
the target that the controller is burst capable and that
the target should not arbitrarily disconnect after the
first data phase of this operation.
Under certain circumstances, MRAR can be accessed
from the Add-On bus instead of the PCI bus.
2
1
0
0
0
Revision 1.02 – June 27, 2006
AMCC Confidential and Proprietary
Bit
Value
DWORD Address (RO)
Read Transfer Address (R/W)
Data Book