PSD4235G2 datasheet(21/93 Pages) STMICROELECTRONICS

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PSD4000 Series

Preliminary Information

The

PSD4000

Functional

Blocks

(cont.)

9.1.1.4 Power-Up Condition

The PSD4000 internal logic is reset upon power-up to the read array mode. The FSi and

CSBOOTi select signals, along with the write strobe signal, must be in the false state

during power-up for maximum security of the data contents and to remove the possibility of

data being written on the first edge of a write strobe signal. Any write cycle initiation is

locked when VCC is below VLKO.

9.1.1.5 Read

Under typical conditions, the microcontroller may read the Flash, or secondary Flash

memories using read operations just as it would a ROM or RAM device. Alternately, the

microcontoller may use read operations to obtain status information about a program or

erase operation in progress. Lastly, the microcontroller may use instructions to read

special data from these memories. The following sections describe these read functions.

9.1.1.5.1 Read the Contents of Memory

Main Flash and secodary Flash memories are placed in the read array mode after

power-up, chip reset, or a Reset Flash instruction (see Table 8). The microcontroller can

read the memory contents of main Flash or secondary Flash by using read operations any

time the read operation is not part of an instruction sequence.

9.1.1.5.2 Read the Main Flash Memory Identifier

The main Flash memory identifier is read with an instruction composed of 4 operations:

3 specific write operations and a read operation (see Table 8). The PSD4000 main Flash

memory ID is E8h. The Secondary Flash does not support this instruction.

9.1.1.5.3 Read the Flash Memory Sector Protection Status

The Flash memory sector protection status is read with an instruction composed of 4

operations: 3 specific write operations and a read operation (see Table 8). The read

operation will produce 01h if the Flash sector is protected, or 00h if the sector is not

protected.

The sector protection status for all NVM blocks (main Flash or secondary Flash) can also

be read by the microcontroller accessing the Flash Protection and Flash Boot Protection

registers in PSD I/O space. See section 9.1.1.9.1 for register definitions.

9.1.1.5.4 Read the Erase/Program Status Bits

The PSD4000 provides several status bits to be used by the microcontroller to confirm

the completion of an erase or programming instruction of Flash memory. These status bits

minimize the time that the microcontroller spends performing these tasks and are defined

in Table 9. The status byte resides in even location and can be read as many times as

needed. Please note DQ15-8 is even byte for Motorola MCUs with 16 bit data bus.

FSi/

CSBOOTi

DQ7

DQ6

DQ5

DQ4

DQ3

DQ2

DQ1

DQ0

Data

Toggle

Error

Erase

Flash

VIH

Polling

Flag

Time-

out

Table 9. Status Bits

NOTES: 1. X = Not guaranteed value, can be read either 1 or 0.

2. DQ15-DQ0 represent the Data Bus bits, D15-D0.

3. FSi/CSBOOTi are active high.

For Flash memory, the microcontroller can perform a read operation to obtain these status

bits while an erase or program instruction is being executed by the embedded algorithm.

See section 9.1.1.6 for details.

FSi/

CSBOOTi

DQ15

DQ14

DQ13

DQ12

DQ11

DQ10

DQ9

DQ8

Data

Toggle

Error

Erase

Flash

VIH

Polling

Flag

Time-

out

Table 9A. Status Bits for Motorola

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