µPD6121, 6122
1. PIN FUNCTIONS
(1) Key input pins (KI0 to KI7), key input/output pins (KI/O0 to KI/O7)
A pull-down resistor is placed between key input pins and a VSS pin. When several keys are pressed
simultaneously, the transmission of the corresponding signals is inhibited by a multiple-input prevention circuit.
In the case of double-key input, transmission is inhibited if both keys are pressed simultaneously (within 36 ms
interval); if not pressed simultaneously, the priority of transmission is first key, then second key.
When a key is pressed, the custom code and data code reading is initiated, and 36 ms later, output to REM output
is initiated. Thus if the key is pressed during the initial 36 ms, one transmission is performed. If a key is kept
pressed for 108 ms or longer, only leader codes are consecutively transmitted until the key is released.
Keys can be operated intermittently at intervals as short as 126 ms (interval between two on’s), making this an
extremely fast-response system.
(2) Resonator connection pins (OSCI, OSCO)
The oscillator starts operating when it receives a key input. Use a ceramic resonator with a frequency between
400 and 500 kHz.
(3) Power-supply pin
The power supply voltage is supplied by two 3-V batteries. A broad range of operating power supply voltage is
allowed, from 2.0 to 3.3 V. The supply current falls below 1 µA when the oscillator is inactive when no keys are
pressed.
(4) REM output pin
The REM output pin outputs the transmission code, which consists of the leader code, custom code (16 bits),
and data code (16 bits) (Refer to 2. NEC TRANSMISSION FORMAT (REM OUTPUT)).
(5) SEL input pin
By controlling D7 of the data code with this pin, the µPD6121 and µPD6122 can transmit 64 and 128 different
data codes, respectively. By connecting the SEL pin to VDD or VSS, D7 is set to “0” or “1”, respectively.
This pin has high-impedance input, therefore be sure to connect it either to VDD or VSS.
(6) CCS input pin
By placing a diode between the CCS pin and the KI/O pin, it is possible to set a custom code. When a diode
is connected, the corresponding custom code is “1”, and when not connected, it is “0”.
(7) LMP output pin
The LMP pin outputs a low-level signal while the REM pin outputs a transmission code.
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NEC [ NEC ]
