User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 14: Serial Configuration Interface Page
415
SMB
US
R
EGISTERS
The SMBus registers are mapped into the internal I/O section of the memory space. They all occupy a 64 bit
wide slot, although in most cases only one or two bytes are implemented. When a register is written its entire
contents must be written, writes that are smaller than the implemented width will result in the register value
becoming UNPREDICTABLE.
Table 289: SMBus Clock Frequency Registers
smb_freq_0 -
00_1006_0010
smb_freq_1 -
00_1006_0018
Bits
Name
Default
Description
12:0
smb_freq_div
13'h7d
The 100 MHz sys_clock is divided by this x 8 to determine the frequency of the
serial clock. The default value is for 100 kHz. The minimum SMBus clock is 10 kHz
which is generated using a value of 1250. For 400 kHz the value for this field is 31.
63:13
notimp
51’bx
Not implemented.
Table 290: SMBus Command Registers
smb_cmd_0 -
00_1006_0030
smb_cmd_1 -
00_1006_0038
Read returns value from previous smbus read command.
Write sets value for next smbus write command.
Bits
Name
Default
Description
7:0
smb_cmd
8'h0
Write
: Low byte of command to be sent following address.
Read
: First byte received in type 5 or 6 extended mode read.
15:8
smb_cmdh
8'h0
Write
: High byte of command to send in extended mode.
Read
: 2nd Byte received in type 6 extended mode read.
63:15
notimp
56'bx
Not Implemented.
Table 291: SMBus Control Registers
smb_control_0 -
00_1006_0060
smb_control_1 -
00_1006_0068
Bits
Name
Default
Description
0
smb_mk
1'b0
When high, enables interrupt if error is high.
1
smb_finish_en
1'b0
When high, an interrupt will be generated when busy transitions from high to low.
The interrupt is cleared by reading the
smb_status
register.
3:2
reserved
6'h0
Reserved
4
smb_data_out
1'b0
Driven to data pin in direct mode if smb_data_dir is set.
5
smb_data_dir
1'b0
Data direction in direct mode, set for output clear to turn driver off.
6
smb_clk_out
1'b0
Driven to clock pin in direct mode
7
smb_direct
1'b0
Set to enable direct control of clock and data lines (from bits 6:4).
63:8
notimp
56’bx
Not implemented.