Motor de Búsqueda de Datasheet de Componentes Electrónicos |
|
ST6262C Datasheet(PDF) 17 Page - STMicroelectronics |
|
ST6262C Datasheet(HTML) 17 Page - STMicroelectronics |
17 / 78 page 17/78 ST62T52C ST62T62C/E62C CPU REGISTERS (Cont’d) However, if the program space contains more than 4096 bytes, the additional memory in program space can be addressed by using the Program Bank Switch register. The PC value is incremented after reading the ad- dress of the current instruction. To execute relative jumps, the PC and the offset are shifted through the ALU, where they are added; the result is then shifted back into the PC. The program counter can be changed in the following ways: - JP (Jump) instructionPC=Jump address - CALL instructionPC= Call address - Relative Branch Instruction.PC= PC +/- offset - Interrupt PC=Interrupt vector - ResetPC= Reset vector - RET & RETI instructionsPC= Pop (stack) - Normal instructionPC= PC + 1 Flags (C, Z). The ST6 CPU includes three pairs of flags (Carry and Zero), each pair being associated with one of the three normal modes of operation: Normal mode, Interrupt mode and Non Maskable Interrupt mode. Each pair consists of a CARRY flag and a ZERO flag. One pair (CN, ZN) is used during Normal operation, another pair is used dur- ing Interrupt mode (CI, ZI), and a third pair is used in the Non Maskable Interrupt mode (CNMI, ZN- MI). The ST6 CPU uses the pair of flags associated with the current mode: as soon as an interrupt (or a Non Maskable Interrupt) is generated, the ST6 CPU uses the Interrupt flags (resp. the NMI flags) instead of the Normal flags. When the RETI in- struction is executed, the previously used set of flags is restored. It should be noted that each flag set can only be addressed in its own context (Non Maskable Interrupt, Normal Interrupt or Main rou- tine). The flags are not cleared during context switching and thus retain their status. The Carry flag is set when a carry or a borrow oc- curs during arithmetic operations; otherwise it is cleared. The Carry flag is also set to the value of the bit tested in a bit test instruction; it also partici- pates in the rotate left instruction. The Zero flag is set if the result of the last arithme- tic or logical operation was equal to zero; other- wise it is cleared. Switching between the three sets of flags is per- formed automatically when an NMI, an interrupt or a RETI instructions occurs. As the NMI mode is automatically selected after the reset of the MCU, the ST6 core uses at first the NMI flags. Stack. The ST6 CPU includes a true LIFO hard- ware stack which eliminates the need for a stack pointer. The stack consists of six separate 12-bit RAM locations that do not belong to the data space RAM area. When a subroutine call (or inter- rupt request) occurs, the contents of each level are shifted into the next higher level, while the content of the PC is shifted into the first level (the original contents of the sixth stack level are lost). When a subroutine or interrupt return occurs (RET or RETI instructions), the first level register is shifted back into the PC and the value of each level is popped back into the previous level. Since the accumula- tor, in common with all other data space registers, is not stored in this stack, management of these registers should be performed within the subrou- tine. The stack will remain in its “deepest” position if more than 6 nested calls or interrupts are execut- ed, and consequently the last return address will be lost. It will also remain in its highest position if the stack is empty and a RET or RETI is executed. In this case the next instruction will be executed. Figure 7ST6 CPU Programming Mode l SHORT DIRECT ADDRESSING MODE VREGISTER WREGISTER PROGRAM COUNTER SIX LEVELS STACK REGISTER CZ NORMAL FLAGS INTERRUPT FLAGS NMI FLAGS INDEX REGISTER VA000423 b7 b7 b7 b7 b7 b0 b0 b0 b0 b0 b0 b11 ACCUMULATOR YREG. POINTER X REG. POINTER CZ CZ |
Número de pieza similar - ST6262C |
|
Descripción similar - ST6262C |
|
|
Enlace URL |
Política de Privacidad |
ALLDATASHEET.ES |
¿ALLDATASHEET es útil para Ud.? [ DONATE ] |
Todo acerca de Alldatasheet | Publicidad | Contáctenos | Política de Privacidad | Intercambio de Enlaces | Lista de Fabricantes 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 |