On 29/08/2021 14:17, Peter Maydell wrote:
On Sun, 29 Aug 2021 at 11:07, Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> wrote:According to the "Z80X30 Register Reset Values" table in the ESCC datasheet bits 2 and 6 are set whilst bits 0 and 1 are cleared during channel reset. All other bits should be left unaltered. Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> --- hw/char/escc.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/hw/char/escc.c b/hw/char/escc.c index 63e0f15dfa..0f6957ba8b 100644 --- a/hw/char/escc.c +++ b/hw/char/escc.c @@ -281,12 +281,11 @@ static void escc_reset_chn(ESCCChannelState *s) s->wregs[W_MISC2] = MISC2_PLLDIS; /* Enable most interrupts */ s->wregs[W_EXTINT] = EXTINT_DCD | EXTINT_SYNCINT | EXTINT_CTSINT | - EXTINT_TXUNDRN | EXTINT_BRKINT; + EXTINT_TXUNDRN | EXTINT_BRKINT;This indentation fix should probably have been in the coding-style-fixes patch.
Okay I can do that.
+ s->rregs[R_STATUS] &= ~(STATUS_RXAV | STATUS_ZERO); + s->rregs[R_STATUS] |= STATUS_TXEMPTY | STATUS_TXUNDRN; if (s->disabled) { - s->rregs[R_STATUS] = STATUS_TXEMPTY | STATUS_DCD | STATUS_SYNC | - STATUS_CTS | STATUS_TXUNDRN; - } else { - s->rregs[R_STATUS] = STATUS_TXEMPTY | STATUS_TXUNDRN; + s->rregs[R_STATUS] |= STATUS_DCD | STATUS_CTS; } s->rregs[R_SPEC] = SPEC_BITS8 | SPEC_ALLSENT;We seem to use this function for both 'channel reset' and 'hardware reset' -- escc_reset just calls escc_reset_chn for each channel, and is used as the DeviceState::reset as well as for the 'hardware reset' you get by writing to WR9 with both D6 and D7 set to 1. Because we want this software-triggered 'hardware reset' to not reset all registers to fixed values, I think we need to disentangle the power-on reset DeviceState::reset so that power-on reset always brings the device back to exactly the state that it has when QEMU first starts.
I'm currently struggling to understand what the initial power-on values are for the ESCC registers. According to the reset table both 'hardware reset' and 'software reset' don't change the values of all bits which implies the power-on state is different, but I can't seem to find a description of it anywhere? Could we assume that all ESCC registers are initialised to zero, and the guest will perform a suitable reset during driver initialisation?
ATB, Mark.
