IBM EM78M611E manual Control Register, Sampling Rate and Debounce Length

EM78M611E

Universal Serial Bus Series Microcontroller

Pattern Detect Application (PDA) can calculate the length of one pattern and interrupt the MCU while the serial signal is transiting from high to low (or vise-versa). Then the MCU reads the length value from a specified register.

8.9.2 Control Register

The PDA includes an enable control bit, one control register and 4-length counter registers in 0x10 ~0x13.

IOCA [2] PDA Enable Control Bit

When this bit is set, the PDA function starts and the P92 and P93 become input pin automatically to sample the serial signal.

0 : disable PDA function

1 : enable PDA function

RB (PDA Control Register) Default Value: (0B_0000_0000)

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

SE2.F

SE1.F

SR.2

SR.1

SR.0

DB2

DB1

DB0

This register is used to define two parameters of PDA function; signal sampling rate and debounce length. When a pattern ends, the value in the counter is loaded into its respective register and the RB[6] or RB[7] is set to indicate which type of pattern (high or low) is at its end or which type of pattern counter is on overflow.

0: low pattern

1: high pattern

R10 (P.92 Low Pattern Counter)

This register records the length of P.92 in low status.

R11 (P.92 High Pattern Counter)

This register records the length of P.92 in high status.

R12 (P.93 Low Pattern Counter)

This register record the length of P.93 in low status.

R13 (P.93 High Pattern Counter)

This register records the length of P.93 in high status.

R10~R13 function as general registers if this function is not enabled. Once the enabled bit is set, these four registers will be loaded with the value of the pattern counter.

8.9.3 Sampling Rate and Debounce Length

Although the two-pattern detect pins are separate, and each pin has its own pattern counter, both pins use the same Sampling Rate and Debounce Length parameters.

The PDA samples the serial signal every fixed interval. The pattern counter will be incremented by one at sampling time if the signal remains unchanged. If the signal is at

26 • Product Specification (V1.1) 11.22.2006

(This specification is subject to change without further notice)