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38D5 Datasheet(PDF) 51 Page - Renesas Technology Corp |
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38D5 Datasheet(HTML) 51 Page - Renesas Technology Corp |
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51 / 142 page  Rev.3.04 May 20, 2008 Page 51 of 134 REJ03B0158-0304 38D5 Group Fig. 42 Structure of AD control register ADKEY function The ADKEY function is used to judge the analog input voltage input from the ADKEY pin. When the A/D converter starts operating after VIL (0.7 × Vcc-0.5) or less is input, the event of analog voltage input can be judged with the A/D conversion interrupt. This function can be used with the STP and WIT state. As for the ADKEY function in 38D5 Group, the A/D conversion of analog input voltage immediately after starting ADKEY function is not performed. Therefore, the A/D conversion result immediately after an ADKEY function is undefined. Accordingly, when the A/D conversion result of the analog input voltage input from the ADKEY pin is required, start the A/D conversion by program after the analog input pin corresponding to ADKEY is selected. • ADKEY Selection When the ADKEY pin is used, set the ADKEY selection bit to “1”. The ADKEY selection bit is “0”, just after the A/D conversion is started. • ADKEY Enable The ADKEY function is enabled by writing “1” to the ADKEY enable bit. Surely, in order to enable ADKEY function, set “1” to the ADKEY enable bit, after setting the ADKEY selection bit to “1”. When the ADKEY enable bit of the AD control register is “1”, the analog input pin selection bits become invalid. Please do not write “0” in the AD conversion completion bit by the program during ADKEY enabled state. [ADKEY Control Circuit] In order to obtain a more exact conversion result, by the A/D conversion with ADKEY, execute the following; • set the input to the ADKEY pin into a steep falling waveform, • stabilize the input voltage within 8 clock cycles (1 µs at f(XIN) = 8 MHz) after the input voltage is under VIL The threshold voltage with an actual ADKEY pin is the voltage between VIH-VIL. In order not to make ADKEY operation perform superfluously in a noise etc., in the state of the waiting for an input, set the voltage of an ADKEY pin to VIH (0.9VCC) or more. When the following operations are performed, the A/D conversion operation cannot be guaranteed. • When the CPU mode register is operated during A/D conversion operation, • When the AD conversion control register is operated during A/D conversion operation, • When the STP or WIT instruction is executed during A/D conversion operation. AD control register (ADCON: address 001516) Analog input pin selection bits b2 b1 b0 0 0 0 : P50/AN0 0 0 1 : P51/AN1 0 1 0 : P52/AN2 0 1 1 : P53/AN3 1 0 0 : P54/AN4 1 0 1 : P55/AN5 1 1 0 : P56/AN6 1 1 1 : P57/AN7 AD conversion completion bit 0 : Conversion in progress 1 : Conversion completed AD conversion clock selection bit 0 : φSOURCE/2 1 : φSOURCE/8 ADKEY enable bit 0 : Disabled 1 : Enabled 10-bit or 8-bit conversion switch bit 0 : 10-bit AD 1 : 8-bit AD ADKEY selection bit 0 : Invalid 1 : Valid b7 b0 *VREF input switch bit 0: ON only during A/D conversion 1: ON Note : The bit 5 to bit 1 of address 001616 become “0” at reading. Also, bit 0 is undefined at reading. (low-order) * b1 b0 b7 b0 AD conversion register high-order (Address 001716) b7 b2 b3 b6 b5 b4 b9 b8 (high-order) b7 b0 At 10bitAD (Read address 001716 before 001616) b5 b0 b1 b4 b3 b2 b7 b6 b7 b0 Notes 1: φSOURCE indicates the followings: •XIN input in the frequency/2, 4, or 8 mode •On-chip oscillator divided by 4 in the low-speed and the on-chip oscillator mode 2: When the ADKEY enable bit is “1”, the analog input pin selection bits are invalid. Do not execute the A/D conversion by program while the ADKEY is enabled. Bit 0 to bit 2 of ADCON are not changed even when ADKEY is enabled. AD conversion register low-order (Address 001616) At 8bitAD (Read only address 001716) (Address 001716) (2) (1) |
Similar Part No. - 38D5_08 |
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Similar Description - 38D5_08 |
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