PSD4235G2 datasheet(65/93 Pages) STMICROELECTRONICS

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PSD4000 Series

Preliminary Information

9.6.1 Standard JTAG Signals

The JTAG configuration bit (non-volatile) inside the PSD can be set by the user in the

PSDsoft. Once this bit is set and programmed in the PSD, the JTAG pins are dedicated to

JTAG at all times and is in compliance with IEEE 1149.1. After power up the standard

JTAG signals (TDI, TDO TCK and TMS) are inputs, waiting for a serial command from an

external JTAG controller device (such as FlashLink or Automated Test Equipment). When

the enabling command is received from the external JTAG controller, TDO becomes an

output and the JTAG channel is fully functional inside the PSD. The same command that

enables the JTAG channel may optionally enable the two additional JTAG pins, TSTAT

and TERR.

The PSD4000 supports JTAG ISP commands, but not Boundary Scan. ST’s PSDsoft

software tool and FlashLink JTAG programming cable implement these JTAG-ISP

commands.

9.6.2 JTAG Extensions

TSTAT and TERR are two JTAG extension signals enabled by a JTAG command received

over the four standard JTAG pins (TMS, TCK, TDI, and TDO). They are used to speed

programming and erase functions by indicating status on PSD pins instead of

having to scan the status out serially using the standard JTAG channel. See Application

Note 54.

TERR will indicate if an error has occurred when erasing a sector or programming a byte in

Flash memory. This signal will go low (active) when an error condition occurs, and stay

low until a special JTAG command is executed or a chip reset pulse is received after an

“ISC-DISABLE” command.

TSTAT behaves the same as the Rdy/Bsy signal described in section 9.1.1.2. TSTAT will

be high when the PSD4000 device is in read array mode (Flash memory and Boot Block

contents can be read). TSTAT will be low when Flash memory programming or erase

cycles are in progress, and also when data is being written to the Secondary Flash Block.

TSTAT and TERR can be configured as open-drain type signals with a JTAG command.

9.6.3 Security and Flash Memories Protection

When the security bit is set, the device cannot be read on a device programmer or through

the JTAG Port. When using the JTAG Port, only a full chip erase command is allowed.

All other program/erase/verify commands are blocked. Full chip erase returns the part to a

non-secured blank state. The Security Bit can be set in PSDsoft.

All Flash Memory and Boot sectors can individually be sector protected against erasures.

The sector protect bits can be set in PSDsoft.

The

PSD4000

Functional

Blocks

(cont.)

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