LM8333EVALKIT National Semiconductor, LM8333EVALKIT Datasheet - Page 14

• Manufacturer Part Number: LM8333EVALKIT
• Description: BOARD EVALUATION LM8333
• Manufacturer: National Semiconductor

Specifications of LM8333EVALKIT

• Main Purpose: Interface, Special Purpose
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: LM8333
• Primary Attributes: Mobile I/O Companion with Key-Scan, I/O Expansion, PWM, Access.bus Host
• Secondary Attributes: Board has MCU for USB to PC GUI
• Lead Free Status / RoHS Status: Not applicable / Not applicable

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10.5 COMMAND EXECUTION SUMMARY
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With the interrupt, status, and error codes, the LM8333
provides the features needed to support a reliable key-
scan functionality.
Up to 14 key-scan events can be stored in an internal FIFO
buffer. The end of buffer is indicated with the 00 (empty
character) code.
The host can repeatedly read the FIFO without modifying
the FIFO pointer using the RPT_FIFO_READ command
(0x21), for example if an error is encountered during a
read.
The LM8333 asserts the IRQ output low when a new
character is pressed after the last interrupt acknowledge
from the host. The IRQ output will be deasserted after the
host has acknowledged the interrupt by reading the
interrupt code using the READ_INT command (0xD0).
The host can synchronize with the LM8333 by reading the
status code with the READ_STAT command (0xE0). The
status code verifies whether the last command was
successfully completed.
Two GPIO pins on the LM8333 may be configured as
external interrupt inputs. A rising or falling edge on an
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enabled interrupt input triggers wake-up from Halt mode
and asserts an interrupt to the host by pulling the IRQ
output low.
The host can change the debounce time from the default
time of 10 ms. This can be used for reliable scanning of
keyboards with noisy contacts. The debounce time can be
set to about 1 second in steps of 4 milliseconds. The
debounce time is set with the DEBOUNCE command
(0x22).
The host can change the active time permitted before
entering Halt mode from the default period of 500 ms. The
active time is the time during which the keypad is scanned
after the last key is released, before entering Halt mode.
The active time must be longer than the debounce time.
The host can program the direction and output state of four
general-purpose I/O pins. The host can also read the
states on these pins.
The host can program a 16-bit timer for generating a PWM
output. If the PWM function is not used, the PWM pin can
be used as a general-purpose output.