3.11
Additional Features / Extended Registers
This chapter describes the extended registers in the I/O address space necessary for programming the
additional features of the VP7. The extended register set is specific to the VP7. To protect the system
against illegal accesses to these registers, the extended registers set can be locked completely. Writing
$05 to the Lock Register LOCKR enables access, writing $04 disables access to the extended
configuration register set.
Software using the Extended Reg. Set must comply to the methods described in M-PGM_IOPNPSYS.
7
6
5
4
3
2
1
0
LOCKR
I/O
Lock Register
$169
W
LBP[]
Lock Bit Pattern. Writing $05 to this register enables access to the extended
registers. Writing $04 disables access to this registers. Any other values have
no effect. The values written can not be read back.
3.11.1
SMB bus devices
The VP7 uses a serial 2-wire bus to communicate with several onboard devices:
Device
Designator
SMB address (binary)
Clock generator (*)
U1000
1101000X
PIX4 slave port (*)
U1700
0001000X
Serial EEprom (24C04)
U1991
1010100X
Temperature sensor (LM75)
U1992
1001111X
SDRAM bank 0 (*)
U1400
1010000X
SDRAM bank 1 (*)
U1401
1010001X
The Temperature sensor from National Semiconductor LM75 is located close to the processor
and therefore has a comparable temperature.
In the serial EEprom 24C04 a board identifier or other board unique information can be stored.
For details on accessing these devices see the appropriate data sheets.
For further information see data sheet of LM75 and 24C04.
Access to devices marked by (*) is done by BIOS. It is strongly recommended not to access these
devices by user software.
3.11.1.1
Temperature Sensor
A National Semiconductors LM75 temperature sensor is implemented on the VP7 board. Its interface is
connected to the I2C control signals of the SMB. The sensor is located below the CPU and shows the air
temperature between board and CPU. The sensor has an over-temperature output integrated, which can
be used to take actions like reducing the CPU speed.
More information can be found in the LM75 datasheet from National Semiconductors.
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