Solution:

====Question==== In the following program, the printer status reported by system is different between PCA-6144V and PCA-6145L. Why? > sample.c #include #include #define _BIOS_IBMPC #include #define STATUS 2 /* ?????????? */ #define PORTNUM 0 /* LPT1 ????? */ int main(void) { int status, abyte = 0; printf("????????????????????????\n"); getch(); status = biosprint(STATUS, abyte, PORTNUM); if (status & 0x08) printf("I/O ??\n"); return 0; } ====Answer==== Please read the attachment first. The function call - "biosprint()" in C language is to call INT 17h (BIOS interrupt call). And the INT 17h read the "printer status" from "status port" of onboard super I/O chip. You customer got the bit 3 (D3 /PD3) via "biosprint() " and check if there is an error having been detected. The most important point is - the ERROR signal must be provided by a printer (see description of pin functions). If this is floating (no connection), the signal of this pin may be any state (it depends on super I/O chip) and it doesn't mean any thing. I have made a table as following, it tells you how the "I/O error" message is transmitted from printer port to C language. State: Printer - error pin High Low Not connect to the printer port Super I/O printer port - error pin High Low Maybe High or Low or tri-state. (it depends on I/O chip) Super I/O status port - error bit High Low Corresponding to super I/O printer port - error pin. INT 17 - BIOS call (the error bit is inverted by INT 17) Low High Corresponding to status port - error bit. biosprint() Low High Corresponding to INT 17 return value We don't know why your customer check the error bit without connecting a printer, but please tell your customer the error bit should be used while connecting a printer to print port because the signal needs be provided by printer.