LPC47M14X datasheet(95/205 Pages) SMSC

95 / 205 page

SMSC DS – LPC47M14X

Page 95

Rev. 03/19/2001

Table 47 illustrates the AT and PS/2 (including Model 30) configuration registers available and the type of access

permitted. In order to maintain software transparency, access to all the registers must be maintained. As Table 47

shows, two sets of registers are distinguished based on whether their access results in the part remaining in powerdown

state or exiting it.

Access to all other registers is possible without awakening the part.

These registers can be accessed during

powerdown without changing the status of the part. A read from these registers will reflect the true status as shown in

the register description in the FDC description. A write to the part will result in the part retaining the data and

subsequently reflecting it when the part awakens. Accessing the part during powerdown may cause an increase in the

power consumption by the part. The part will revert back to its low power mode when the access has been completed.

Pin Behavior

The LPC47M14x is specifically designed for systems in which power conservation is a primary concern. This makes the

behavior of the pins during powerdown very important.

The pins of the LPC47M14x can be divided into two major categories: system interface and floppy disk drive interface.

The floppy disk drive pins are disabled so that no power will be drawn through the part as a result of any voltage applied

to the pin within the part's power supply range. Most of the system interface pins are left active to monitor system

accesses that may wake up the part.

Table 47 – PC/AT and PS/2 Available Registers

AVAILABLE REGISTERS

BASE + ADDRESS

PC-AT

PS/2 (MODEL 30)

ACCESS PERMITTED

Access to these registers DOES NOT wake up the part

00H

----

SRA

01H

----

SRB

02H

DOR (1)

R/W

03H

---

04H

DSR (1)

06H

---

07H

DIR

07H

CCR

Access to these registers wakes up the part

04H

MSR

05H

Data

R/W

Note 1: Writing to the DOR or DSR does not wake up the part, however, writing any of the motor enable bits or doing a

software reset (via DOR or DSR reset bits) will wake up the part.

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