HT6221A HOLTEK [Holtek Semiconductor Inc], HT6221A Datasheet - Page 4

• Manufacturer Part Number: HT6221A
• Description: Multi-Purpose Encoders
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Functional Description
Keyboard Scan
The devices remain in the halt mode during the standby
state (at this time, the oscillator stops, and the standby
current<1 A). The HT6220A consists of 30 active keys,
HT6221A has 32 active keys, HT6221B has 48 active
keys, and the HT6222A has 64 active keys. The key-
board forms of the devices are shown below.
Rev. 1.10
The HT6220A keyboard form
The HT6221A keyboard form
The HT6221B keyboard form
Timing 1. Output Format for the DOUT
HT6220A/HT6221A/HT6221B/HT6222A
4
When one of the keys (30, 32, 48 or 64 keys) is triggered
for over 36ms, the oscillator is enabled and the chip is acti-
vated. 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 ad-
dress 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 (2.24ms) 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 devices are facilitated with 36ms starting time.
The HT6221A/HT6221B/HT6222A also provide three
double-key active functions (K21+K22, K21+K23, and
K21+K24) for tape deck recording operations. The dou-
ble-key operation rules are shown in timing 4 and timing
6.
Transmission Codes
The transmission codes of the devices 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 in-
verse code of the 8-bit data codes. The following is an il-
lustration of the transmission codes.
The HT6222A keyboard form
June 1, 2010