SDA6000 Datasheet, PDF(131/380 Page) Infineon Technologies AG – Teletext Decoder with Embedded 16-bit Controller

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SDA6000 Datasheet, PDF (131/380 Pages) Infineon Technologies AG – Teletext Decoder with Embedded 16-bit Controller

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SDA 6000

System Control & Configuration

Active

Mode

Denied

CPU Interrupt Request

Accepted

IDLE Instruction

Idle

Mode

Denied PEC Request

Executed

PEC Request

UED11132

Figure 6-2 Transitions between Idle Mode and Active Mode

Any interrupt request, whose individual Interrupt Enable flag was set before Idle mode

was entered, will terminate Idle mode regardless of the current CPU priority. The CPU

will not go back into Idle mode when a CPU interrupt request is detected, even when the

interrupt was not serviced because of a higher CPU priority or a globally disabled

interrupt system (IEN = â0â). The CPU will only go back into Idle mode when the interrupt

system is globally enabled (IEN = â1â) and a PEC service on a priority level higher than

the current CPU level is requested and executed.

Note: An interrupt request which is individually enabled and assigned to priority level 0

will terminate Idle mode. However, the associated interrupt vector will not be

accessed.

The watchdog timer may be used to monitor the Idle mode: an internal reset will be

generated if no interrupt request occurs before the watchdog timer overflows. To prevent

the watchdog timer from overflowing during Idle mode it must be programmed to a

reasonable time interval before Idle mode is entered.

Power Down Mode

Clocking of all internal blocks is stopped in Power Down Mode, the contents of the

internal RAMs, however, are preserved through the voltage supplied via the VDD pins.

The watchdog timer is stopped in Power Down Mode. This mode can only be terminated

by an external hardware reset, e.g. by asserting a low level on the RSTIN pin. This reset

will initialize all SFRs and ports to their default state, but will not change the contents of

the internal RAMs.

SDRAM Refreshing

Before entering into one of the power save modes the external SDRAM must be put into

self-refresh-mode by use of register EBIDIR (see Chapter 4.5).

Users Manual

6 - 14

2000-06-15

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