Silan

Semiconductors

SC3010

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

Rev: 2.1

2002-02-28

6

b). Single System Mode (SMS=High)

In the Single System Mode, the KI-Sense Inputs are also pulled High by the p-channel pull-up transistors, as in the

Combined System Mode. The C-Sense Inputs, however, are disabled by switching off their pull-high transistors. A

system code is provided by a wired connection between the C-KO Matrix. The debounce cycle can ONLY be started

by any legal key operation in the KI-KO Matrix. Once the key contact has been established for 18-bit time without

any interruption, the Oscillator-Enable Signal is latched and the key may be released. Any interruption during the 18-

bit time period resets the internal action.

At the end of the debounce cycle, the pull-up transistors in the KI-Lines are then switched off and the pull-up

transistors in the C-lines are turned ON for the first scan cycle. The wired connection in the C-matrix matrix is then

translated into a system number and stored in the system latch. At the end of the first scan cycle, 1) the C-Input pull-

up transistors are switched off and the inputs are again disabled, 2) KI-Sense Input pull-up transistors are turned on.

The command number is generated by the second scan cycle. This command number is then latched and

transmitted together with the system number.

5.KEY RELEASE DETECTION

An additional control bit is complemented after key release. This additional control bit tells the decoder that the

next code is a new command. This feature is important in cases where more digits are needed to be inputted (i.e.

Teletext channel numbers or Viewdata pages). The extra control bit will only be complemented after the completion

of at least one code transmission. The scan cycles are repeated before every code transmission; thus, even with the

Take Over of key operation during the code transmission, the correct system and command numbers are generated.

6.RESETTING THE DEVICE

The device will immediately reset under the following conditions:

1). A key is released during the debounce time

2). A key is released between two codes

3). During Matrix Scanning

a). A key is released while one of the drivers outputs is in the low ohmic state (Logic 0)

b). A key is released before that key has been detected.

c). There is no wired connection in the C-KO Matrix when SMS is in High State.