IPC@CHIP Documentation - SC12 @CHIP-RTOS V1.10

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b) The current stack must be pre-initialized for math emulation:
void my_emu1st(void)
{
asm{
mov word ptr ss:[0x2f],0x0065 // set end of FPU stack
mov word ptr ss:[0x31],0x0125 // set start of FPU stack
mov word ptr ss:[0x27],0 // no protected mode
mov byte ptr ss:[0x26],0 // no 8087
}
}
c) Before executing floating point arithmetic, call the Borland library function _fpreset, which
initializes the stack for floating point emulation.
Example for a task function:
void huge my_task(void)
{
float a;
my_emu1st();
_fpreset();
// ..... ready for executing floating point arithmetic
}
If you are interest in more details, take a look at the Borland 5.02 RTL sources (fpinit.asm).
We will provide an example for using floating point arithmetic in separate tasks or within CGI
callbacks.
3. Using Math emulation with Borland C++ 5.02 (also for older versions of Borland C) produces a
conflict between the NMI interrupt of the @CHIP-RTOS (Interrupt Vector 0x02) and the Borland
floating exception handling. Borland C math emulation also uses INT 2 for generating floating
point exceptions. Our internal NMI interrupt service function (normally called at power fail case)
will no longer execute during the runtime of the user's application. We have provided a solution
which moves the Borland exception function from INT 2 to another interrupt vector. We modified
the Borland RTL source (fpinit.asm) and include the modifications directly into the application
project. It is planned to provide an example in our Internet download area.
Configure PPP client or server
1. Connected modems should be configured in chip.ini with the modem command ATE0 INITCMD.
This prevents the modem from echoing characters to the peer in command mode. The COM and
the serial ports of the IPC@CHIP have only 4 lines (TxD/RxD/CTS/RTS) and no line for detecting
a hang-up of the modem. Because of this fact we provided the Idletimeout and the
MODEMCTRL configuration features in chip.ini or in the PPP client init structure type. But the
idletimeout and modemctrl detection can fail if a modem has switched its echo mode on. If
the peer modem hangs up without correctly closing a PPP session, the IPC@chip modem also
hangs up and goes into the command mode. Because of the missing line for detecting a modem
hang-up, the PPP server doesn't know anything about the broken connection and still sends PPP
frames to the modem. It can happen that the modem echoes these characters back to the
IPC@CHIP due to being in "Echo on" mode. This will cause the idletimeout to not work.
2. We recommend that the PPP server or client and the connected modems should run (if possible)
with RTS/CTS flow control (see chip.ini flow control mode or the PPP client init structure type).
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