ELANSC310 datasheet(59/119 Pages) AMD

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Élan™SC310 Microcontroller Data Sheet

PREL IMINARY

ALTERNATE PIN FUNCTIONS

To provide the system designer with the most flexibility,

the ÉlanSC310 microcontroller provides a means for

reconfiguring some of the pin functions, depending on

the system requirements. Reconfiguration of the

ÉlanSC310 microcontroller pin functions is accom-

plished in one of two ways, depending on the pin func-

tions that are to be reconfigured. To select the CPU

local bus interface or maximum ISA bus interface, the

state of the DTR and RTS pins are sampled on the ris-

ing edge of the RESIN and IORESET signals when

power is first applied to the ÉlanSC310 microcontroller.

This is shown in Figure 8.

After power has been initially applied and RESIN and

IORESET are deasserted, additional assertions of

IORESET while RESIN = 1 will not cause the pin con-

figurations to change. However, the pin configuration

inputs are always sampled in response to RESIN as-

sertions. Table 26 shows the pin states at reset to en-

able the two different pin configurations involving the

Local Bus and Maximum ISA Bus. The bus configura-

tion selected can be read in bits 5–6 of the Memory

Configuration 1 Register, Index 66h, after the reset.

The second method of reconfiguring ÉlanSC310 micro-

controller pin functions is accomplished by program-

ming the internal configuration registers. This method

is used to configure the following functions:

n DRAM or SRAM main memory interface

n Unidirectional or bidirectional parallel port

n Clock source driving the X1OUT[BAUDOUT] pin

n 14.336-MHz clock

Table 26.

Bus Option Select Bit Logic

Bus Selected

DTR/CFG1

RTS/CFG0

Local Bus

Full/Maximum ISA

VCC

RESIN and

IORESET

RTS

DTR

DTR and RTS sampled at

the rising edge of RESIN and IORESET

Notes:

This is shown to illustrate when CFG0 and CFG1 are sampled and is not intended to be used for reset timings. For reset timings,

refer to Table 45 on page 88.

Figure 8.

Bus Option Configuration Select

ELANSC310 Datasheet(PDF) 59 Page - Advanced Micro Devices

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