Specifications

Élan™SC310 Microcontroller Data Sheet 59
PRELIMINARY
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
10
Full/Maximum ISA
11
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