DS80C410 Datasheet, PDF (76/102 Pages) Dallas Semiconductor – Network Microcontrollers with Ethernet and CAN

DS80C410/DS80C411 Network Microcontrollers with Ethernet and CAN
Serial Loader
The serial loader function implemented by the firmware can be invoked by leaving the serial loader pin (P1.7) at
logic 1 during the boot sequence. When this condition is found, the ROM monitors the RXD0 pin for reception of
the <CR> character (0Dh) at a supported baud rate. The serial loader function uses hardware serial port 0 in mode
1 (asynchronous, one start bit, eight data bits, no parity, and one stop bit in full duplex). The serial loader can
automatically detect certain baud rates and configure itself to that speed. The equation below is used to calculate
the nearest integer-reload value for Timer 2 (used for serial port 0 baud rate generation) based on the external
clock frequency and desired baud rate. The calculated (nearest integer) RCAP2H, RCAP2L reload value may not
result in an exact baud rate match. The calculated reload value and clock frequency can be used in the equation to
solve for the baud rate configurable by the DS80C410. It is advised that the baud rate mismatch be no greater than
±2.5% to maintain reliable communication. The functionality was designed to work for clock rates from 3.680MHz to
75.000MHz and baud rates from 2400 to 115,200.
RCAP2H, RCAP2L = 65,536 - ^{Oscillator Clock Frequency}
32 x Baud Rate
For example, suppose an 18MHz crystal is being used and a 19,200 baud rate is desired. The above equation
yields a nearest integer reload value of FFE3h. This reload value results in a true baud rate of 19396.6 (+1% error).
Once a supported baud rate has been detected, the DS80C410 transmits an ASCII text banner containing
copyright information and prompt for command entry. At this point, the user can issue any of the supported serial
loader commands. A summary of the supported serial loader commands can be seen in Table 15. A detailed
description of each command and further information pertaining to the serial loader can be found in the High-Speed
Microcontroller Userís Guide: Network Microcontroller Supplement.
Table 15. Serial Loader Command Summary
COMMAND
B
C
D
E
F
G
H, ?
L
N
V
T2
T8
X
Z
FUNCTION
Bank select
CRC-16 of memory range
Dump Intel hex data from selected bank
Exit the loader and try to execute code
Fill selected bank memory with hex data
Go: Start executing code at offset 0 in the current bank
Help: Display ROM version and current bank
Load Intel hex into memory
NetBoot
Verify memory against incoming hex
Enable clock doubler
Enable/Disable load of internal 64kByte RAM
Execute code at a given offset in the current bank
Zap: Erase/clear the current bank.
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