CS5530 datasheet(59/241 Pages) NSC

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Functional Description (Continued)

3.4.2.3

Save-To-Disk

Save-to-Disk is supported by the CS5530. In this state,

the power is typically removed from the CS5530, causing

the state of the legacy peripheral devices to be lost.

Shadow registers are provided for the devices which

allows their state to be saved prior to removing power.

This is necessary because the legacy AT peripheral

devices used several write only registers. In order to

restore the exact state of these devices on resume, the

write only register values are “shadowed” so that the val-

ues can be saved by the Power Management Software.

The PC/AT compatible floppy port is not part of the

CS5530. However, it is expected that one will be attached

on the ISA bus in a SuperI/O or by some other means.

Some of the FDC registers are shadowed because they

cannot be safely read. They are shown in Table 3-15.

Additional shadow registers for other functions are

described in:

• Table 3-39 "DMA Shadow Register" on page 93

• Table 3-41 "PIT Shadow Register" on page 95

• Table 3-44 "PIC Shadow Register" on page 97

• Table 3-52 "Real-Time Clock Registers" on page 104

Table 3-15. Power Management Shadow Registers

Bit

Description

F0 Index B4h

Floppy Port 3F2h Shadow Register (RO)

Reset Value = 00h

7:0

Floppy Port 3F2h Shadow (Read Only): Last written value of I/O Port 3F2h. Required for support of FDC power

ON/OFF and Zero Volt Suspend/Resume coherency.

This register is a copy of an I/O register which cannot safely be directly read. Value in register is not deterministic of when

the register is being read. It is provided here to assist in a Save-to-Disk operation.

F0 Index B5h

Floppy Port 3F7h Shadow Register (RO)

Reset Value = 00h

7:0

Floppy Port 3F7h Shadow (Read Only): Last written value of I/O Port 3F7h. Required for support of FDC power

ON/OFF and Zero Volt Suspend/Resume coherency.

This register is a copy of an I/O register which cannot safely be directly read. Value in register is not deterministic of when

the register is being read. It is provided here to assist in a Save-to-Disk operation.

F0 Index B6h

Floppy Port 1F2h Shadow Register (RO)

Reset Value = 00h

7:0

Floppy Port 1F2h Shadow (Read Only): Last written value of I/O Port 1F2h. Required for support of FDC power

ON/OFF and Zero Volt Suspend/Resume coherency.

This register is a copy of an I/O register which cannot safely be directly read. Value in register is not deterministic of when

the register is being read. It is provided here to assist in a Save-to-Disk operation.

F0 Index B7h

Floppy Port 1F7h Shadow Register (RO)

Reset Value = 00h

7:0

Floppy Port 1F7h Shadow (Read Only): Last written value of I/O Port 1F7h. Required for support of FDC power

ON/OFF and Zero Volt Suspend/Resume coherency.

This register is a copy of an I/O register which cannot safely be directly read. Value in register is not deterministic of when

the register is being read. It is provided here to assist in a Save-to-Disk operation.

CS5530 Datasheet(PDF) 59 Page - National Semiconductor (TI)

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