45111 datasheet(170/184 Pages) ETC2

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15 Appendix E: SX Data Sheet

Page 170

• SX-Key/Blitz Development System Manual 2.0 • Parallax, Inc.

15.3.2.8

CMP_B – Comparator Enable Register

Comparator Enable, 0 = enabled, 1 = disabled

Comparator Output Enable, 0 = enabled, 1 = disabled

Rsvd

Reserved for future use

RES

Comparator Result (EN must = 0)

15.3.3 Port C Registers

There are four registers used to configure the I/O pins of Port C. The TRIS_C register configures the

data direction of the Port C pins as input or output. The LVL_C register configures the input pins as

TTL or CMOS voltage level. The PLP_C register enables/disables pull up resistors on Port C input pins.

The ST_C register enables/disables the Schmitt-Trigger inputs on Port C input pins. To access these

registers you must first write a particular value to the MODE register. Please refer to

Table 32 – SX20/28

Mode Register

to find the values required in the MODE register to access the Port C Registers. Note: All

the bits in the following registers are set to ‘1’ on power up.

15.3.3.1

TRIS_C – Data Direction Register

A bit set to ‘1’ in this register sets the corresponding I/O port pin to input (high z) mode.

A bit set to ‘0’ in this register sets the corresponding I/O port pin to output mode.

15.3.3.2

LVL_C - TTL/CMOS Select Register

A bit set to ‘1’ in this register sets the input level of the corresponding port pin to TTL.

A bit set to ‘0’ in this register sets the input level of the corresponding port pin to CMOS.

OE Rsvd Rsvd Rsvd Rsvd Rsvd RES

CMP_B

RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0

TRIS_C

RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0

LVL_C

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