Start of coin mech handler

diff --git a/ROM2/coinmech.c b/ROM2/coinmech.c
index 80a11a7..a5a38e0 100644 (file)
--- a/ROM2/coinmech.c
+++ b/ROM2/coinmech.c
@@ -1,2 +1,78 @@
 #include "vend.h"
 
+#define COINMECH_ID   0x20
+
+u8 last_byte;
+
+
+u8 parity_test(u8 c) {
+       u8 parity = 0;
+       for (parity = 0; c; c = c>>1) {
+               if (c&1) parity = !parity;
+       }
+       return parity;
+}
+
+/*
+ * parity_good truth table:
+ *
+ *      | parity_test(c)
+ *      | 0   1
+ * -----+---------
+ * R8 0 | 1   0
+ *    1 | 0   1
+ */
+
+bool parity_good(u8 c) {
+       u8 R8 = (_io_ports[M6811_SCCR1] & M6811_R8)?1:0;
+       u8 p = parity_test(c)?1:0;
+       return R8 == p;
+}
+
+void send_byte(u8 c) {
+       last_byte = c;
+       while (!(_io_ports[M6811_SCSR] & M6811_TDRE)); /* wait for TD register empty */
+
+       if (parity_of(c))
+               bset(&_io_ports[M6811_SCCR1], M6811_T8);
+       else
+               bclr(&_io_ports[M6811_SCCR1], M6811_T8);
+}
+
+void ask_for_retrans() {
+       /* sends an 0xff down the line */
+       send_byte(0xff);
+}
+
+
+u8 packet_pos = 0;
+
+#define IS_CTRL(x) (x & 0x10) /* true if this packet is a control packet */
+void sci_interrupt() {
+       u8 in;
+       in = _io_ports[M6811_SCDR];
+       
+       /* test for framing errors & parity bit */
+       if (_io_ports[M6811_SCSR] & M6811_FE || !parity_good(in)) {
+               _io_ports[M6811_SCDR]; /* read of register req'd to clear FE */
+               ask_for_retrans();
+               return;
+       }
+
+       /* all bytes must have the correct ID in the 3 MSBs */
+       if (in & 0xe0 != COINMECH_ID) return;
+
+       /* we have a good packet */
+       if (in == 0x3f) {
+               /* retransmit was requested */
+               send_byte(last_byte);
+               return;
+       }
+
+       if (packet_pos != 0 && !IS_CTRL(x&0x10)) {
+               switch (in & 0x0f) {
+               }
+       } else {
+
+       }
+}