Precision Analog to Digital Converter with Microcontroller and Flash Memory User's Guide

Circuit Descriptions
3-11
Operation
3.4 Circuit Descriptions
The MSC1211EVM combines the MSC1211 microcontroller, 128K RAM, the
ADS8325, 256K EEPROM, a 22.1184MHz crystal, support for two serial ports,
and other support circuits to aid in the evaluation of the MSC1211.
3.4.1 MSC1211
The MSC1211 (U5) is clocked by the 22.1184MHz crystal oscillator, unless it
is disabled with switch SW3–6. When the oscillator is disabled, the MSC1211
can use crystal X1 to provide the clock source using on–chip circuitry, although
oscillator X2 must be removed from the board for reliable crystal operation. In-
puts come from J4 through current-limiting resistors R1–R9.
Programs can be loaded into the 32K bytes of flash memory using the serial
port (Serial0). The MSC1211 has 1,380 bytes of on–chip RAM. Extra RAM is
available through the use of the 128K RAM (U9). 64K of RAM is directly ad-
dressable, with P1.4 providing the means for bank switching.
For detailed information about the MSC1211, consult the MSC1211 product
datasheet (SBAS267) located at www.ti.com.
3.4.2 Programming and Host Communication
The Raisonance integrated software environment (RIDE) and the TI Down-
loader program make for a convenient system of program development,
download, and execution.
Full source code for the MSC1211EVM firmware is included on the CD-ROM.
3.4.3 Power Supply
Power is brought into the board through external power connectors JMP5
(pins 2 and 3) and JMP6 (pins 2 and 3), battery connector B1, or unregulated
power input J6. If a wall power adaptor is plugged into J6, the battery is discon-
nected.
Power supplied from the battery or through J6 is regulated by voltage regu-
lators U3, and U4, which provide +5V digital and +5V analog supplies.
Power supplied from the external connectors (JMP5 and JMP6) is not fil-
tered; regulated power of the correct voltages must be supplied to these
connectors.
The board is laid out with separate analog and digital power supplies. Ana-
log power is 5V and is supplied from regulator U3, or external power con-
nector JMP5. 5V digital power is supplied from regulator U4 or JMP6.
When the external power connector J6 is used, it supplies regulator U3 and
U4.