ADP315PC87570 National Semiconductor, ADP315PC87570 Datasheet - Page 60

• Manufacturer Part Number: ADP315PC87570
• Description: Keyboard and Power Management Controller
• Manufacturer: National Semiconductor

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3. Perform two write operations with data 00h to the same
Once the initial setting of the configuration registers is suc-
cessfully completed, it cannot be set again until reset is ap-
plied. Figure 5-7 illustrates the flow of the PnP protocol
described above.
Two addresses of the host bus I/O address space are used
to access the configuration registers. These addresses hold
the Configuration Index and the Configuration Data Regis-
ter pair. The address of these registers is defined by the
SBAH and SBAL Registers.
The configuration Index Register points to the configuration
register that is read, or written, by a read or write operation
from/to the Data Register, respectively.
5.13.2 Operation Guidelines
Changing Data
One write operation is required to change the contents of a
configuration register.Use one of the following procedures
for changing data in the configuration registers.
Modify Only
1. Write to the Index Register the index of the configuration
2. Write the new data for the configuration register to the
Read, Modify, Write
1. Write to the Index Register the index of the configuration
2. Read the contents of that configuration register from the
3. Write the modified data for the configuration register to
Reserved Bits
To maintain compatibility with future chips, the host soft-
ware should avoid modification of reserved bits whenever
the register is written. You can use a read-modify-write se-
quence to preserve the value of reserved bits.
Conflict Notice
When setting the addresses of different devices, ensure
that no two devices are configured to the same address.
Configuring two devices (or a device and the configuration
Index/Data registers) to the same address may have unpre-
dictable results.
address (as used in steps 2 and 3) to reset any other de-
vice that may have been accidentally enabled by the ad-
dress write operations. Software can now access the
configuration Index and Data Registers, for setting the
PC87570 interface according to the system configura-
tion.
register you want to change. For example, write 56h if
you want to modify the FER Register.
configuration Data Register.
register you want to change. For example, write 56h if
you want to modify the FER Register.
Data Register.
the Data Register.
Host Bus Interface (HBI)
60
Changing the Configuration Base Address
This scheme allows the host to change the location of the
SBAH and SBAL Registers. This protocol may be per-
formed whenever access to the configuration registers is
enabled; i.e., after it was first set using the PnP protocol and
if SBALK in the FLR Register is 0.
The address used should meet the following criteria:
When changing the base address, the host should perform
two data write operations as described in “Changing Data”
on page 60. The data writes should be as follows:
1. Update the eight high bits of the configuration Index
2. Update the eight lower bits of the configuration Index
When required, this process may be repeated.
The address loaded into SBAH and SBAL should al-
ways be an even address (i.e., SBAL.0=0, data written
to it is ignored).
The address points to the configuration Index Register,
and the configuration Data Register is at the next con-
secutive address.
Register’s base address, by writing to SBAH.
This updates an internal temporary register. SBAH is
not yet updated. Reading SBAH at this point returns the
data it contained before the write.
The addresses of the Index and Data registers have not
yet changed.
Register’s base address, by writing to SBAL.
This write operation updates both the SBAH and SBAL
registers with the data stored in the temporary register
and the currently written data, respectively.
The addresses of the configuration Index and Data Reg-
isters are now changed.