LM78 National Semiconductor, LM78 Datasheet - Page 28

• Manufacturer Part Number: LM78
• Description: Microprocessor System Hardware Monitor
• Manufacturer: National Semiconductor

www.national.com
6-0
0-4
3-0
5-4
7-6
Bit
Bit
Bit
7
5
6
7
Address A6–A0
Functional Description
13.10 VID/Fan Divisor Register — Address 47h
Power on –
13.11 Serial Bus Address Register — Address 48h
Power on default Serial Bus address
13.12 Chip Reset/ID Register Address 49h
Power on default for the LM78-J
on default for LM78
13.13 POST RAM — Address 00h–1Fh
The address pointer for the POST RAM auto-increments when written to at Port x0h or x4h. Once the address pointer reaches
1Fh, a FIFO overflow interrupt will be generated and the FIFO will stop incrementing. Normal reads via Port x5h and x6h
auto-increment a separate pointer, and will not cause a FIFO overflow interrupt.
13.14 Value RAM — Address 20h–3Fh or 60h–7Fh (auto-increment)
Serial Bus
Address
Reserved
Chip Reset
Device ID
VID
FAN1 RPM
Control
FAN2 RPM
Control
20h
21h
22h
23h
24h
25h
26h
27h
28h
Reserved
Reserved
<
Name
Name
Name
3:0
<
7:4
>
>
is 0101, and
<
7:0
Address A6–A0 with
>
Read Only
Read/Write
Read/Write
Read/Write
Auto-Increment
Read/Write
Read Only
= 0000 0000.
Read/Write
Read Only
Read/Write
Read/Write
Read Only
Read Only
<
60h
61h
62h
63h
64h
65h
66h
67h
68h
<
7:0
3:0
>
<
>
6:0
(Continued)
= 0100 0000; Power
is mapped to VID
>
The VID
FAN1 Speed Control.
FAN2 Speed Control.
<
<
<
<
<
<
<
<
5:4
5:4
5:4
5:4
7:6
7:6
7:6
7:6
= 0101101 and
Serial Bus address
A one will reset all the registers of the LM78 to the power on default state.
When set the latest version of the LM78 the LM78-J is being used. When cleared
designates the old version of LM78.
>
>
>
>
>
>
>
>
= 00 - divide by 1;
= 01 - divide by 2;
= 10 - divide by 4;
= 11 - divide by 8.
= 00 - divide by 1;
= 01 - divide by 2;
= 10 - divide by 4;
= 11 - divide by 8.
IN0 reading
IN1 reading
IN2 reading
IN3 reading
IN4 reading
-IN5 reading
-IN6 reading
Temperature reading
FAN1 reading
<
3:0
>
<
inputs
3:0
<
28
7
>
>
<
= 0 binary
6:0
>
Description
Description
Description
Description