MEC1322 datasheet(353/456 Pages) MICROCHIP

353 / 456 page

 2014 - 2015 Microchip Technology Inc.

DS00001719D-page 353

MEC1322

30.10 Description

During scanning the firmware sequentially drives low one of the rows (KSO[17:0]) and then reads the column data line

(KSI[7:0]). A key press is detected as a zero in the corresponding position in the matrix. Keys that are pressed are

debounced by firmware. Once confirmed, the corresponding keycode is loaded into host data read buffer in the 8042

Host Interface module. Firmware may need to buffer keycodes in memory in case this interface is stalled or the host

requests a Resend.

30.10.1

INITIALIZATION OF KSO PINS

If the Keyboard Scan Interface is not configured for PREDRIVE Mode, KSO pins should be configured as open-drain

outputs. Internal or external pull-ups should be used so that the GPIO functions that share the pins do not have a floating

input when the KSO pins are tri-stated.

If the Keyboard Scan Interface is configured for PREDRIVE Mode, KSO pins must be configured as push-pull outputs.

Internal or external pull-ups should be used to protect the GPIO inputs associated with the KSO pins from floating inputs.

30.10.2

PREDRIVE MODE

There is an optional Predrive Mode that can be enabled to actively drive the KSO pins high before switching to open-

drain operation. The PREDRIVE ENABLE bit in the Keyscan Extended Control Register is used to enable the PRE-

DRIVE option. Timing for the Predive mode is shown in Section 38.9, Keyboard Scan Matrix Timing.

30.10.2.1

Predrive Mode Programming

The following precautions should be taken to prevent output pad damage during Predrive Mode Programming.

FIGURE 30-2:

Keyboard Scan Interface Block Diagram

KSO

Select

KSO[17:0]

KSI Input

and

Status

Registers

KSI[7:0]

KSI

Interrupt

Interface

Output

Decoder

KSC_INT

KSC_INT_WAKE

48MHz

VCC1_RESET

SPB

I/F

EC Bus

MEC1322 Datasheet(PDF) 353 Page - Microchip Technology

MEC1322 Datasheet(HTML) 353 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL