Noise Considerations, Preventing AutoStore

Figure 13. Current versus Cycle Time

(mA)	50
(mA)
Current	40
Current	30
Active	20	Writes
		Writes
Average
Average	10	Reads
	10	Reads
	0

50100 150 200 300 Cycle Time (ns)

Noise Considerations

The STK14D88 is a high-speed memory and so must have a high-frequency bypass capacitor of 0.1 µF connected between both VCC pins and VSS ground plane with no plane break to chip VSS. Use leads and traces that are as short as possible. As with all high-speed CMOS ICs, careful routing of power, ground, and signals will reduce circuit noise.

Document Number: 001-52037 Rev. **

STK14D88

Preventing AutoStore

The AutoStore function can be disabled by initiating an AutoStore Disable sequence. A sequence of READ operations is performed in a manner similar to the software STORE initi- ation. To initiate the AutoStore Disable sequence, the following sequence of E controlled or G controlled READ operations must be performed:

1.Read Address 0x0E38, Valid READ

2.Read Address 0x31C7, Valid READ

3.Read Address 0x03E0, Valid READ

4.Read Address 0x3C1F, Valid READ

5.Read Address 0x303F, Valid READ

6.Read Address 0x03F8, AutoStore Disable

The AutoStore can be re-enabled by initiating an AutoStore Enable sequence. A sequence of READ operations is performed in a manner similar to the software RECALL initiation. To initiate the AutoStore Enable sequence, the following sequence of E controlled or G controlled READ operations must be performed:

1.Read Address 0x0E38, Valid READ

2.Read Address 0x31C7, Valid READ

3.Read Address 0x03E0, Valid READ

4.Read Address 0x3C1F, Valid READ

5.Read Address 0x303F, Valid READ

6.Read Address 0x07F0, AutoStore Enable

If the AutoStore function is disabled or re-enabled, a manual STORE operation (Hardware or Software) needs to be issued to save the AutoStore state through subsequent power down cycles. The part comes from the factory with AutoStore enabled.

In all cases, make sure the READ sequence is uninterrupted. For example, an interrupt that occurs in the sequence that reads the nvSRAM would abort this sequence, resulting in an error.

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