ELANSC310 AMD [Advanced Micro Devices], ELANSC310 Datasheet - Page 56

• Manufacturer Part Number: ELANSC310
• Description: Single-Chip, 32-Bit, PC/AT Microcontroller
• Manufacturer: AMD [Advanced Micro Devices]

Local Bus or Maximum ISA Bus Controller
D e p e n d i n g o n t h e c o n fi g u r a t i o n c h o s e n , th 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-
56
PIRQ0(IRQ3)
PIRQ1(IRQ6)
IRQ1
IOCHRDY
IOCS16
MCS16
IRQ14
DTR/CFG1
RTS/CFG0
IORESET
IRQ15
IRQ4
IOCHCHK
PULLUP
Signal Name
Table 25. External Resistor Requirements
Élan™SC310 Microcontroller Data Sheet
P R E L I M I N A R Y
Pin No.
194
193
195
192
196
197
198
140
182
173
177
183
92
93
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
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.
Pull Up
100K
10K
10K
10K
10K
10K
10K
10K
1K
1K
1K
1K
Local Bus
Down
100K
Pull
10K
Pull Up
100K
10K
10K
10K
10K
10K
10K
10K
Maximum ISA
1K
1K
1K
1K
Down
100K
Pull
10K
Notes
1
1
50%