ELANSC310 datasheet(56/119 Pages) AMD

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Élan™SC310 Microcontroller Data Sheet

PREL IMINARY

Local Bus or Maximum ISA Bus Controller

Depending on the con f i gur ation cho s en, t h e

ÉlanSC310 microcontroller’s pin functionality will differ.

The two different options are Local Bus and Maximum

ISA Bus modes. The pin options are selected upon

power-up reset. (See “Alternate Pin Functions” on

page 59.) Only Local Bus or Maximum ISA Bus mode

is available in a particular design. Local bus mode

does, however, provide a subset of the ISA bus. For

more information, see “Maximum ISA Interface versus

Local Bus Interface” on page 60.

Local Bus Option

The local bus interface is integrated with the memory

controller and the ISA bus controller, and it permits fast

transfers to and from external local bus peripherals,

such as video controllers. The local bus option is basi-

cally an Am386SXLV microprocessor local bus with an

LDEV, LRDY, and CPUCLK added. Additional local bus

signals are available in this mode and are described in

“Local Bus Interface” on page 35.

Maximum ISA Bus Option

The Maximum ISA option provides the most ISA bus

signals of either of the ÉlanSC310 microcontroller bus

options. Since master cycles and ISA refresh are not

necessary in handheld designs, the ÉlanSC310 micro-

controller does not provide these signals in either bus

mode. The SYSCLK output from the ÉlanSC310 micro-

controller is a clock that is normally only used for the

external keyboard controller if one exists. This clock is

9.2 MHz and can be stopped completely.

This clock is not related to any of the ISA bus cycle tim-

ings. The ISA bus cycle timings vary depending on the

clock speed selected for the internal ISA bus clock.

Internal Resistors

The ÉlanSC300 microcontroller’s internal pull-down

and pull-up resistors are approximately 100-K

Ω ± 50%

tolerance. They don’t provide the level of termination

that may be necessary to meet design noise margins or

the timing and termination requirements for different

bus specifications (e.g., ISA bus or local bus).

The internal pull-up and pull-down resistors only pro-

vide adequate termination for when the input is floating

and is in a very low noise environment, or for systems

where power consumption is too critical to allow for the

additional current associated with stronger pullups. Be-

cause of this, it is recommended that the designer use

the external pull-up and pull-down resistors (shown in

Table 25) on signals with critical timing or noise immu-

nity requirements. The external pull-up and pull-down

resistors are also recommended for additional design

margin, provided that space and power consumption

are not major issues.

Table 25.

External Resistor Requirements

Signal Name

Pin No.

Local Bus

Maximum ISA

Notes

Pull Up

Pull

Down

Pull Up

Pull

Down

PIRQ0(IRQ3)

194

10K

PIRQ1(IRQ6)

193

10K

IRQ1

195

10K

IOCHRDY

192

IOCS16

196

MCS16

197

IRQ14

198

10K

DTR/CFG1

10K

100K

RTS/CFG0

100K

10K

IORESET

140

10K

IRQ15

182

10K

IRQ4

173

10K

IOCHCHK

177

PULLUP

183

100K

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