General-Purpose Static RAM (SRAM)MPC5644A Microcontroller Reference Manual, Rev. 6Freescale Semiconductor 213Chapter 11General-Purpose Static RAM (SRAM)11.1 IntroductionThe MPC5644A includes 192 KB of general-purpose SRAM. The first 32 KB of SRAM is powered by itsown power supply pin during standby operation.11.2 FeaturesThe SRAM controller includes these features:• Supports read/write accesses mapped to the SRAM memory from any master• 32-KB block powered by separate supply for standby operation• Byte, halfword, word and doubleword addressable• 7-bit ECC11.3 Modes of operation11.3.1 Normal (Functional) modeAllows reads and writes of the SRAM memory arrays.11.3.2 Standby modePreserves contents of the standby portion of the memory when the 1.2 V (VDD) power drops below thelevel of the standby power supply voltage. There are two possible supplies for standby: 1.0 V directly fromthe VSTBY pin and 2 – 5 volts (also on the VSTBY pin), which enables a standby regulator.VSTBY pad needs an external RC to slower the ramp to atleast 100 us to prevent a false ESD trigger.Updates to the standby portion of the SRAM are inhibited during system reset or during Standby Mode.11.4 Block diagramThe SRAM block diagram is shown in Figure 11-1.Figure 11-1. SRAM Block DiagramSRAM160 KB VSTBY32 KBVDDStandby Switch
