 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
P12C508 Datasheet(PDF) 29 Page - Microchip Technology |
|
|
|||||||||||||||||||||||||||||
P12C508 Datasheet(HTML) 29 Page - Microchip Technology |
|
|
29 / 84 page  © 1996 Microchip Technology Inc. Advance Information DS40139A-page 29 PIC12C5XX TABLE 7-4: RESET CONDITION FOR SPECIAL REGISTERS STATUS Addr: 03h PCL Addr: 02h Power on reset 0001 1xxx 1111 1111 MCLR reset during normal operation 000u uuuu 1111 1111 MCLR reset during SLEEP 0001 0uuuu 1111 1111 WDT reset during SLEEP 0000 0uuu 1111 1111 WDT reset normal operation 0000 1uuu 1111 1111 Wake-up from SLEEP on pin change 1001 0uuu 1111 1111 Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’. 7.3.1 MCLR ENABLE This configuration bit when unprogrammed (left in the ‘1’ state) enables the external MCLR function. When programmed, the MCLR function is tied to the internal VDD, and the pin is assigned to be a GPIO. See Figure 7-7. FIGURE 7-7: MCLR SELECT 7.4 Power-On Reset (POR) The PIC12C5XX family incorporates on-chip Power- On Reset (POR) circuitry which provides an internal chip reset for most power-up situations. A Power-on Reset pulse is generated on-chip when VDD rise is detected (in the range of 1.5V - 2.1V). To take advantage of the POR, tie the MCLR pin directly to VDD. An internal weak pull-up resistor is imple- mented using a transistor. Refer to Table 10-5 for the pull-up resistor ranges. This will eliminate external RC components usually needed to create a Power-on Reset. A maximum rise time for VDD is specified. See Electrical Specifications for details. When the device starts normal operation (exits the reset condition), device operating parameters (voltage, frequency, temperature, ...) must be met to ensure operation. If these conditions are not met, the device must be held in reset until the operating parameters are met. A simplified block diagram of the on-chip Power-On Reset circuit is shown in Figure 7-8. GP3/MCLR/VPP MCLRE INTERNAL MCLR WEAK PULL-UP The Power-On Reset circuit and the Device Reset Timer (Section 7.5) circuit are closely related. On power-up, the reset latch is set and the DRT is reset. The DRT timer begins counting once it detects MCLR to be high. After the time-out period, which is typically 18 ms, it will reset the reset latch and thus end the on- chip reset signal. A power-up example where MCLR is tied to VSS is shown in Figure 7-9. VDD is allowed to rise and stabilize before bringing MCLR high. The chip will actually come out of reset TDRT msec after MCLR goes high. In Figure 7-10, the on-chip Power-On Reset feature is being used (MCLR and VDD are tied together). The VDD is stable before the start-up timer times out and there is no problem in getting a proper reset. However, Figure 7-11 depicts a problem situation where VDD rises too slowly. The time between when the DRT senses a high on the GP3/MCLR/VPP pin, and when the GP3/MCLR/VPP pin (and VDD) actually reach their full value, is too long. In this situation, when the start- up timer times out, VDD has not reached the VDD (min) value and the chip is, therefore, not guaranteed to function correctly. For such situations, we recommend that external RC circuits be used to achieve longer POR delay times (Figure 7-10). For additional information refer to Application Notes “ Power-Up Considerations” - AN522 and “Power-up Trouble Shooting” - AN607. Note: When the device starts normal operation (exits the reset condition), device operat- ing parameters (voltage, frequency, tem- perature, etc.) must be meet to ensure operation. If these conditions are not met, the device must be held in reset until the operating conditions are met. |
|
Link URL |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link to Datasheet | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
