HT6221 Holtek Semiconductor Inc., HT6221 Datasheet - Page 5

• Manufacturer Part Number: HT6221
• Description: Ht6221/ht6222 -- Multi-purpose Encoders
• Manufacturer: Holtek Semiconductor Inc.

Functional Description
Keyboard Scan
The HT6221/HT6222 remain in the halt mode during the
standby state (at this time, the oscillator stops, and the
standby current<1 A). The HT6221 consists of 32 ac-
tive keys, and the HT6222 has 64 active keys. The key-
board forms of the HT6221/ HT6222 are shown below.
The output code carrier of the DOUT pin is shown in Timing 2:
Rev. 1.50
The HT6221 keyboard form
The HT6222 keyboard form
Output format for the DOUT
38kHz carrier
5
When one of the keys (32 or 64 keys) is triggered for over
36ms, the oscillator is enabled and the chip is activated. If
the key is pressed and held for 108ms or less, the 108ms
transmission codes are enabled and comprised of a
header code (9ms), an off code (4.5ms), low byte address
codes (9ms~18ms), high byte address codes
(9ms~18ms), 8-bit data codes (9ms~18ms), and the in-
verse codes of the 8-bit data codes (18ms~9ms). After the
pressed key is held for 108ms, if the key is still held down,
the transmission codes turn out to be a composition of
header (9ms) and off codes (2.5ms) only.
To avoid mistakes made by keyboard scanning or simul-
taneous two-key inputs (except for the three double-key
active functions (K21+K22, K21+K23, and K21+K24),
the HT6221/HT6222 are facilitated with 36ms starting
time.
The HT6221/HT6222 also provide three double-key ac-
tive functions (K21+K22, K21+K23, and K21+K24) for
tape deck recording operations. The double-key opera-
tion rules are shown in timing 4 and timing 6.
Transmission Codes
The transmission codes of the HT6221/HT6222 consist
of a 9ms header code, a 4.5ms off code, 16-bit address
codes (18ms~36ms), 9ms~18ms 8-bit data codes, and
the inverse code of the 8-bit data codes. The following is
an illustration of the transmission codes:
HT6221/HT6222
October 1, 2007