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ATtiny5 数据表(PDF) 12 Page - ATMEL Corporation |
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ATtiny5 数据表(HTML) 12 Page - ATMEL Corporation |
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12 / 168 page  12 8127C–AVR–10/09 ATtiny4/5/9/10 4.8 Register Description 4.8.1 CCP – Configuration Change Protection Register • Bits 7:0 – CCP[7:0] – Configuration Change Protection In order to change the contents of a protected I/O register the CCP register must first be written with the correct signature. After CCP is written the protected I/O registers may be written to dur- ing the next four CPU instruction cycles. All interrupts are ignored during these cycles. After these cycles interrupts are automatically handled again by the CPU, and any pending interrupts will be executed according to their priority. When the protected I/O register signature is written, CCP[0] will read as one as long as the pro- tected feature is enabled, while CCP[7:1] will always read as zero. Table 4-1 shows the signatures that are in recognised. 4.8.2 SPH and SPL — Stack Pointer Register 4.8.3 SREG – Status Register • Bit 7 – I: Global Interrupt Enable The Global Interrupt Enable bit must be set for the interrupts to be enabled. The individual inter- rupt enable control is then performed in separate control registers. If the Global Interrupt Enable Register is cleared, none of the interrupts are enabled independent of the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt has occurred, and is set by the RETI instruction to enable subsequent interrupts. The I-bit can also be set and cleared by the application with the SEI and CLI instructions, as described in the document “AVR Instruction Set” and “Instruction Set Summary” on page 151. Bit 7 6 5432 10 0x3C CCP[7:0] CCP Read/Write W WWW WWWW Initial Value 0 0 0000 00 Table 4-1. Signatures Recognised by the Configuration Change Protection Register Signature Group Description 0xD8 IOREG: CLKMSR, CLKPSR, WDTCSR Protected I/O register Bit 151413121110 9 8 0x3E SP15 SP14 SP13 SP12 SP11 SP10 SP9 SP8 SPH 0x3D SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0 SPL 765 43210 Read/Write R/W R/W R/W R/W R/W R/W R/W R/W Read/Write R/W R/W R/W R/W R/W R/W R/W R/W Initial Value RAMEND RAMEND RAMEND RAMEND RAMEND RAMEND RAMEND RAMEND Initial Value RAMEND RAMEND RAMEND RAMEND RAMEND RAMEND RAMEND RAMEND Bit 7 6 5432 10 0x3F I T H S V N Z C SREG Read/Write R/W R/W R/W R/W R/W R/W R/W R/W Initial Value 0 0 0000 00 |
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