LM78 National Semiconductor, LM78 Datasheet - Page 24

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

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6-0
Bit
Configuration Register
Interrupt Status Register 1
Interrupt Status Register 2
SMI Mask Register 1
SMI Mask Register 2
NMI Mask Register 1
NMI Mask Register 2
VID/Fan Divisor Register
Serial Bus Address Register
Chip Reset/ID Register
POST RAM
Value RAM
Value RAM
7
Functional Description
REGISTERS AND RAM
13.1 Address Register (Port x5h)
The main register is the ADDRESS Register located at Port x5h. The bit designations are as follows:
Address Pointer Index (A6–A0)
(Power On default 0)
Registers and RAM
Address
Pointer
Busy
Bit 7
Busy
Name
Read/Write
Read
Only
Read/
Write
40h
41h
42h
43h
44h
45h
46h
47h
48h
00–1Fh
20–3Fh
60–7Fh
Bit 6
A6–A0 in
A6
Hex
49h
(Continued)
Address of RAM and Registers. See the tables below for detail.
A one indicates the device is busy because of a Serial Bus transaction or another ISA
bus transaction. With checking this bit, multiple ISA drivers can use LM78 without
interfering with each other or a Serial Bus driver.
It is the user’s responsibility not to have a Serial Bus and ISA bus operations at the
same time.
This bit is:
Set: with a write to Port x5h or when a Serial Bus transaction is in progress.
Reset: with a write or read from Port x6h if it is set by a write to Port x5h, or when the
Serial Bus transaction is finished.
Bit 5
A5
0000 1000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
0100 0000
0010 1101
0100 0000
<
<
7:4
3:0
Power On Value of
>
>
<
= 0101;
= VID3–VID0
7:0
Registers:
Address Pointer (Power On default 00h)
>
Bit 4
24
A4
in Binary
Bit 3
A3
Description
Auto-increment to the address of Interrupt
Status Register 2 after a read or write to
Port x6h.
Auto-increment to the address of SMI Mask
Register 2 after a read or write to Port x6h.
Auto-increment to the address of NMI Mask
Register 2 after a read or write to Port x6h.
Auto-increment to the next location after a
read or write to Port x6h and stop at 1Fh.
Auto-increment to the next location after a
read or write to Port x6h and stop at 7Fh.
Bit 2
A2
Notes
Bit 1
A1
Bit 0
A0