PSD835G2 datasheet(77/102 Pages) STMICROELECTRONICS

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PSD835G2

JTAG Extensions

TSTAT and TERR are two JTAG extension signals

enabled by an JTAG command received over the

four standard JTAG signals (TMS, TCK, TDI, and

TDO). They are used to speed Program and Erase

cycles by indicating status on PSD signals instead

of having to scan the status out serially using the

standard JTAG channel. See Application Note

AN1153.

TERR indicates if an error has occurred when

erasing a sector or programming a Byte in Flash

memory. This signal goes Low (active) when an

Error condition occurs, and stays Low until a spe-

cial JTAG command is executed or a chip Reset

(RESET)

pulse

received

after

“ISC_DISABLE” command.

TSTAT behaves the same as Ready/Busy de-

scribed

the

section

entitled

Ready/Busy

(PE4), page 26. TSTAT is High when the PSD de-

vice is in READ mode (primary and secondary

Flash memory contents can be read). TSTAT is

Low when Flash memory Program or Erase cycles

are in progress, and also when data is being writ-

ten to the secondary Flash memory.

TSTAT and TERR can be configured as open-

drain type signals during a JTAG command.

Security and Flash memory 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 and 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 primary and secondary Flash memory sectors

can individually be sector protected against era-

sures. The Sector Protect Bits can be set in PSD-

soft.

Table 48. JTAG Port Signals

Port E Pin

JTAG Signals

Description

PE0

TMS

Mode Select

PE1

TCK

Clock

PE2

TDI

Serial Data In

PE3

TDO

Serial Data Out

PE4

TSTAT

Status

PE5

TERR

Error Flag

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