73m2921 ETC-unknow, 73m2921 Datasheet - Page 12

• Manufacturer Part Number: 73m2921
• Description: Advanced Single Chip Modem
• Manufacturer: ETC-unknow

73M2921
Advanced Single
Chip Modem
An example of a Configuration Register write cycle is shown in figures 2 and 3. Figure 2 shows the activity on the
interface register data pins and
73M2921 responds (the contents of this response are not important to the host). Then the host writes the high
and low byte of the Configuration register to the 73M2921.
An example of the Control and Data bytes for a CRA write is shown in Figure 3. In this example we will write 90
00h to Configuration register one (CR1). This turns on the digital portion of the 73M2921.
The Control byte shows D6 set to indicate that a word size transfer will take place. D5 is zero to indicate a write
will occur. D4 is set to specify Configuration Register Access. D0 of the Control byte is always 1h for
Configuration Register Access. The data byte shows D7 and D5 set to indicate that CR1 is to be accessed. D4 is
always set for configuration register access. D3:0 are always zero for configuration register access.
The response from the 73M2921 will not be defined.
The word size transfer of CR1 data is also shown in figure 3. The MS byte is 90h. This enables the digital portion
of the 73M2921. The LS byte is 0h. Refer to the configuration register description on pages 10 and 11 for further
information.
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MSB
MSB
MSB
LSB
LSB
LSB
0
1
X
X
1
0
1
0
X
X
0
0
FIGURE 3: Write Command and Response
. First there are two command bytes sent by the host processor. The
0
1
X
X
0
0
RESPONSE FROM 73M2921
COMMAND FROM HOST
CR DATA FROM HOST
X
X
1
1
1
0
DATA
DATA
DATA
TDK Semiconductor
0
0
X
X
0
0
X
X
0
0
0
0
0
0
X
X
0
0
X
X
1
0
0
0
WRITE TO
CONFIGURATION
REGISTERS
CHOOSE
CR1
HIGH BYTE
OF CR1
LOW BYTE
OF CR1
Control Byte
Data Byte
February 99 Rev M