BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
362
Section 11: Generic/Boot Bus
Document
1250_1125-UM100CB-R
shows the byte lane correspondences for the generic bus. These are discussed in more detail in the
sections that follow.
C
ONFIGURING
A
C
HIP
S
ELECT
R
EGION
The properties of a chip select region on the generic bus are configured by writing a set of registers. There are
eight sets, denoted by having
_0
to
_7
appended to the register names used in this discussion.
A
DDRESS
R
ANGE
The address range allocated to the generic bus is partitioned by configuring the base address and size of each
region. The base address of the region always has bits [39:30] and [15:0] as zero, bits [29:16] are set in the
io_ext_start_addr
register. This allows the start address to be set on any 64KB boundary below
00_4000_0000
. If the start address is set below the base address of the generic bus range (
00_1009_0000
)
the region is disabled. The region start address is subtracted from addresses as they pass through the bus
interface, so each device sees a contiguous block starting from zero.
T h e s i z e o f t h e r e g i o n i s s e t i n t h e
i o _ e x t _ m u l t _ s i z e
r e g i s t e r . T h e s i z e o f t h e r e g i o n i s
64KB * (
io_ext_mult_size
+1). Since only 12 bits of the register are valid, the minimum region size is 64KB,
and the maximum size is 256MB. An alternative way of thinking about this is that the last address in the region
has bits [39:30] all zero, bits [29:16] equal to
io_ext_start_addr
+
io_ext_mult_size
and bits [15:0] all ones.
If the last address of the region is set above
00_3FFF_FFFF
some of the region will not be accessible.
Table 247: Byte Lanes for the Generic Bus
Mode
IO_AD[31:24]
IO_AD[23:16]
IO_AD[15:8]
IO_AD[7:0]
Non Multiplex
D[7:0]
A[23:16]
A[15:8]
A[7:0]
Multiplex: ALE active
BE[3:0]
A[27:24]
A[23:16]
A[15:8]
A[7:0]
Multiplex: ALE inactive / 8 bit device
D[7:0]
Multiplex: ALE inactive / 16 bit big endian device
D[15:8]
D[7:0]
Multiplex: ALE inactive / 32 bit big endian device
D[31:24]
D[23:16]
D[15:8]
D[7:0]
Multiplex: ALE inactive / 8 bit PCMCIA
D[7:0] CE1#
Multiplex: ALE inactive / 16 bit PCMCIA
D[7:0] CE1#
D[15:8] CE2#
Multiplex: ALE inactive / 16 bit little endian devices
D[7:0]
D[15:8]
Multiplex: ALE inactive / 32 bit little endian devices
D[7:0]
D[15:8]
D[23:16]
D[31:24]
Multiplex: ALE inactive / Alternate 8 bit device
D[7:0]
Parity for byte lane (only on data, not address)
IO_ADP[3]
IO_ADP[2]
IO_ADP[1]
IO_ADP[0]
Multiplex: Offsets i.e. A[1:0]
+0
+1
+2
+3
Byte enable: Active low while ALE active
(Valid for both reads and writes)
IO_AD[31]
IO_AD[30]
IO_AD[29]
IO_AD[28]
Содержание BCM1125
Страница 18: ...BCM1250 BCM1125 BCM1125H User Manual 10 21 02 Broadcom Corporation Page xviii Document 1250_1125 UM100CB R ...
Страница 28: ...BCM1250 BCM1125 BCM1125H User Manual 10 21 02 Broadcom Corporation Page xxviii Document 1250_1125 UM100CB R ...
Страница 515: ...BCM1250 BCM1125 BCM1125H User Manual 10 21 02 Broadcom Corporation Page vii Index Document 1250_1125 UM100CB R ...