escc: fix STATUS_SYNC bit in R_STATUS register

After an SDLC "Enter hunt" command has been sent the STATUS_SYNC bit should remain
high until the flag byte has been detected. Whilst the ESCC device doesn't yet
implement SDLC mode, without this change the active low STATUS_SYNC is constantly
asserted causing the MacOS OpenTransport extension to hang on startup as it thinks
it is constantly receiving LocalTalk responses during its initial negotiation
phase.

Signed-off-by: Mark Cave-Ayland <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Mark Cave-Ayland <[email protected]>

Author: mcayland

hw/char/escc.c

@@ -94,6 +94,7 @@
 #define W_IVEC    2
 #define W_RXCTRL  3
 #define RXCTRL_RXEN    0x01
+#define RXCTRL_HUNT    0x10
 #define W_TXCTRL1 4
 #define TXCTRL1_PAREN  0x01
 #define TXCTRL1_PAREV  0x02
@@ -561,7 +562,13 @@ static void escc_mem_write(void *opaque, hwaddr addr,
                 break;
             }
             break;
-        case W_INTR ... W_RXCTRL:
+        case W_RXCTRL:
+            s->wregs[s->reg] = val;
+            if (val & RXCTRL_HUNT) {
+                s->rregs[R_STATUS] |= STATUS_SYNC;
+            }
+            break;
+        case W_INTR ... W_IVEC:
         case W_SYNC1 ... W_TXBUF:
         case W_MISC1 ... W_CLOCK:
         case W_MISC2 ... W_EXTINT: