Another question concerning the extif: I have read sbextif.h and sbmips.c, where the timing/delay parameters are initialized:
Does anyone (Oleg? ;)) know which timing parameters W0 to W3 are? This seems to be quite different from the BCM1250 (there are far more parameters described in the BCM1250 manual).Code:/* Set programmable interface timing for external uart */
tmp = CEIL(10, ns) << FW_W3_SHIFT; /* W3 = 10nS */
tmp = tmp | (CEIL(20, ns) << FW_W2_SHIFT); /* W2 = 20nS */
tmp = tmp | (CEIL(100, ns) << FW_W1_SHIFT); /* W1 = 100nS */
tmp = tmp | CEIL(120, ns); /* W0 = 120nS */
W_REG(&eir->prog_waitcount, tmp); /* 0x01020a0c for a 100Mhz clock */
The reason I'm asking this is that I want to add not only the (D)UART but maybe also other devices (i2c using a pcf8584 would be nice, some additional GPIO ports using 74ls273, etc...). To do this it is necessary to implement a simple address decoding circuit; the current one is quit inefficient - the lpt port is selected every time A4 is asserted, so it's not only available at 0xbf800010 but at 0xbf800018 as well because A3 is not checked. So if this is properly done the address range from 0xbf800018 to 0xbf80001f would be available for other purposes. The same is true for the range from 0xbf800400 to 0xbf80040f (if the chip select for the UART is only generated when A10 is low) and 0xbf800418 to 0xbf80041f. I have listed only these ranges because A10 and A4 to A0 are all easily accessible from pcb pads or pins and this method would give us 8+16+8=32 memory locations which should be enough for most applications.
I have attached a image, just in case my english wasn't intelligible. ;)
BTW: Technik, have you any opinion whether it really is a 12,75MHz XTAL or rather 13,5MHz? (See post #41)
