Rainbow Electronics T89C5121 - Manual (Page 71)

71
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 8 11.0592 12 14.3 14.7456 16
9600 OK OK OK OK OK OK -
19200 OK - OK OK Ok OK OK
38400 - OK OK OK OK OK
57600 - - OK - OK OK -
115200 - - - - - OK -
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
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