No CIA A interrupt during startup

[dirkwhoffmann]

By comparing Omega's bootstrap output with vAmiga's, I notices that Omega is triggering a CIA A interrupt at some point:

intreq 20
intreq 8008
*** IRQ *** 8

This interrupt does not occur in vAmiga, because vAmiga is yet programmed to crash on the first CIA A interrupt. This is most likely the reason why the hand & disk picture is not drawn.

[dirkwhoffmann]

Omega write into CIA A space at PC = fe982a. This PC is reached before reaching fe89da which is my current standard breakpoint.

vAmiga does not reach fe982a before reaching fe89da.

[dirkwhoffmann]

I started running vAmiga against SAE. The first CIA A accesses read as follows in SAE:

vAmiga reads back:

[83] (156, 26) FC0514: ---- 4004 0020: CIAA: Peek 0 (hex: 00) = 254 (DDRA = 3) [83] (156, 26) FC0514: ---- 4004 0020: CIAA: Poke 00,FC [83] (156, 26) FC0514: ---- 4004 0020: CIAA: ## PA changed: /FIR1: 1 /FIR0: 1 /RDY: 1 /TK0: 1 /WPRO: 1 /CHNG: 1 /LED: 0 OVL: 0

More precisely: vAmiga reads 254 where SAE reads 226:

254 = 11111110
226 = 11100010

Seems like vAmiga needs to invert the disk bits (which is strange, because these bits are marked as active low in the HRM).

[dirkwhoffmann]

Drive identification looks good.

After the identification has been completed, another mismatch happens:

vAmiga reads back 0:

[84] ( 42,181)  FC6D10: --BD 602C 0060: CIAB: Peek 15 (hex: 0F) = 0
[84] ( 42,181)  FC6D10: --BD 602C 0060: CIAB: Poke(15) = 0 (hex: 00)
[84] ( 42,194)  FC6D16: --BD 602C 0060: CIAB: Poke(10) = 0 (hex: 00)
[84] ( 42,200)  FC6D1A: --BD 602C 0060: CIAB: Poke(9) = 0 (hex: 00)

[dirkwhoffmann]

SAE uses 4 as the initial value for the control registers. Strange, because I don't think this reflects what the real hardware does.

ciaacra = ciaacrb = ciabcra = ciabcrb = 0x4;

[dirkwhoffmann]

There seems to be an interesting discrepancy in this region:

[85] (  2, 33)  FE5484: PCBD 602C 0040: CIAA: Poke(14) = 0 (hex: 00)
[85] (  2, 39)  FE5488: PCBD 602C 0040: CIAA: Poke(14) = 0 (hex: 00)
[85] (  2, 45)  FE548E: PCBD 602C 0040: CIAA: Poke(14) = 64 (hex: 40)
[85] (  3, 43)  FC4722: PCBD 202C 0040: CIAA: Poke(13) = 136 (hex: 88)
[85] (  3,191)  FE5498: PCBD 602C 0040: CIAA: Poke(14) = 0 (hex: 00)
[85] ( 29,188)  FE58D0: PCBD 602C 0040: CIAA: Peek 2 (hex: 02) = 3
[85] ( 29,188)  FE58D0: PCBD 602C 0040: CIAA: Poke(2) = 3 (hex: 03)

SAE:

It's not easy to compare both emulators from here on, because VSYNC interrupts start to interfere.

[dirkwhoffmann]

The first IRQ in SAE is a level 3 VSYNC interrupt. It occurs after the second write to BLTSIZE. Same in vAmiga which is good so far ...

[dirkwhoffmann]

I think I'm coming closer. The displayed SAE log shows that the serial port interrupt of CIA A gets enabled during boot (first write statement). After that, a VSYNC interrupt triggers (which has higher priority than the SP interrupt). When the VSYNC int is over, the SP interrupt is performed (level 2 IRQ).

As far as I remember, my CIAs don't implement the SP interrupt, because they are taken from VirtualC64 and the C64 does not really use the serial register. Definitely a smoking gun ...

[dirkwhoffmann]

CIA A triggers keyboard interrupts now. The keyboard behaves like a real Amiga keyboard and sends a POWER_UP_KEY_STREAM id code on startup, followed by a KB_TERMINATE_KEY_STREAM id code.

Next strange sequence is the following in vAmiga:

[85] ( 70,168)  FE931C: PCBD 202C 0040: CIAA: Peek 7 (hex: 07) = 255
[85] ( 70,179)  FE9316: PCBD 202C 0040: CIAA: Peek 8 (hex: 08) = 0
[85] ( 70,189)  FE931C: PCBD 202C 0040: CIAA: Peek 7 (hex: 07) = 255
[85] ( 70,200)  FE9316: PCBD 202C 0040: CIAA: Peek 8 (hex: 08) = 0
[85] ( 70,210)  FE931C: PCBD 202C 0040: CIAA: Peek 7 (hex: 07) = 255
[85] ( 70,221)  FE9316: PCBD 202C 0040: CIAA: Peek 8 (hex: 08) = 0
...

This sequence also appears in SAE, but it seems to terminate faster in SAE.

[dirkwhoffmann]

Fixed