T83C5121XXX-ICSIL datasheet(71/115 Pages) ATMEL

71 / 115 page

A/T8xC5121

4164G–SCR–07/06

Autobaud

The ISP feature allows a wide range of baud rates in the user application. It is also

adaptable to a wide range of oscillator frequencies. This is accomplished by measuring

the bit-time of a single bit in a received character. This information is then used to pro-

gram the baud rate in terms of timer counts based on the oscillator frequency. The ISP

feature requires that an initial character (an uppercase U) be sent to the T8xC5121 to

establish the baud rate. Table show the autobaud capability.

Protection Mechanisms

Transfer Checks

Table 53. Synthesis of the Communication Protection Mechanisms

Notes:

1. The transfer of SSB Byte is also secured by CRC as the CRC is computed on all the

16K data.

2. If a bad transfer has occurred in the Internal EEPROM (CRC is bad), as the CRC

check is finally done at the end of CRAM programming, application program will NOT

be executed after any Reset.

Security

Table 54. Synthesis of the Security Mechanisms

Table 52. Autobaud Performances

Frequency (MHz)

Baudrate (kHz)

6.176

11.0592

14.3

14.7456

9600

19200

38400

57600

115200

-----

Source

Target

Check

UART ISP

MCU

Checksum included in commands is tested with calculated checksum: if

bad, X echo returned to ISP

MCU

CRAM

CRC computed during CRAM Write operation: if error an error code is

applied on P3.7. Error code’Z’ is returned to ISP.

MCU

Intern. EEP

Same protection as above because CRAM is written in sequence after

each page programming of EEP

Source

Target

Case

Protection

UART ISP

Intern. EEP

Read access

SSB level 2 must be set (done, if

selected, at ISP Programming or Ext

EEP Download)

UART ISP

CRAM

Read access

SSB level 2 IN CRAM must be set (SSB

is downloaded from Int EEP after Reset)

UART ISP

Intern. EEP

Partial Programming

which would not fit

with old CRC

SSB level 1 must be set (done, if

selected, at ISP Programming or Ext

EEP Download)

Then the EEP must be, first, erased

before reprogramming.

Programming is done on all the memory

space

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