X-Git-Url: http://gitweb.hugovil.com/?a=blobdiff_plain;f=src%2Fpsw.c;h=09352adafc56f9487723e988adc22c170dca2e62;hb=8d9b71ab3848729da1cf90a38a599be0b08cbb5c;hp=2210d85218982422b5986173351b7a666a831141;hpb=84075f7a1709b2d05858dc5f866fb4e4eb385ce0;p=emu8051.git

diff --git a/src/psw.c b/src/psw.c
index 2210d85..09352ad 100644
--- a/src/psw.c
+++ b/src/psw.c
@@ -22,42 +22,116 @@
 #include "reg8051.h"
 #include "memory.h"
 
+/* Returns 0 or 1 */
+int
+psw_read_bit(int bit)
+{
+	return (memory_read8(INT_MEM_ID, _PSW_) >> bit) & 0x01;
+}
+
 void
-psw_write_cy(int cy)
+psw_write_bit(int bit, int val)
 {
 	u_int8_t psw = memory_read8(INT_MEM_ID, _PSW_);
 
-	if (cy)
-		psw |= 0x80;  /* Set */
+	if (val)
+		psw |= (1 << bit);  /* Set */
 	else
-		psw &= ~0x80; /* Clear */
+		psw &= ~(1 << bit); /* Clear */
 
 	memory_write8(INT_MEM_ID, _PSW_, psw); /* Save updated value */
 }
 
+/* Returns 0 or 1 */
+int
+psw_read_cy(void)
+{
+	return psw_read_bit(PSW_BIT_CY);
+}
+
+void
+psw_write_cy(int cy)
+{
+	psw_write_bit(PSW_BIT_CY, cy);
+}
+
 void
 psw_set_cy(void)
 {
-	u_int8_t psw = memory_read8(INT_MEM_ID, _PSW_);
+	psw_write_bit(PSW_BIT_CY, 1);
+}
 
-	psw |= 0x80;
+void
+psw_clr_cy(void)
+{
+	psw_write_bit(PSW_BIT_CY, 0);
+}
 
-	memory_write8(INT_MEM_ID, _PSW_, psw); /* Save updated value */
+/* Returns 0 or 1 */
+int
+psw_read_ac(void)
+{
+	return psw_read_bit(PSW_BIT_AC);
 }
 
 void
-psw_clr_cy(void)
+psw_write_ac(int ac)
 {
-	u_int8_t psw = memory_read8(INT_MEM_ID, _PSW_);
+	psw_write_bit(PSW_BIT_AC, ac);
+}
 
-	psw &= ~0x80;
+void
+psw_set_ac(void)
+{
+	psw_write_bit(PSW_BIT_AC, 1);
+}
 
-	memory_write8(INT_MEM_ID, _PSW_, psw); /* Save updated value */
+void
+psw_clr_ac(void)
+{
+	psw_write_bit(PSW_BIT_AC, 0);
 }
 
 /* Returns 0 or 1 */
 int
-psw_read_cy(void)
+psw_read_ov(void)
+{
+	return psw_read_bit(PSW_BIT_OV);
+}
+
+void
+psw_write_ov(int ov)
+{
+	psw_write_bit(PSW_BIT_OV, ov);
+}
+
+void
+psw_set_ov(void)
+{
+	psw_write_bit(PSW_BIT_OV, 1);
+}
+
+void
+psw_clr_ov(void)
+{
+	psw_write_bit(PSW_BIT_OV, 0);
+}
+
+/*
+ * Compute parity of bits in accumulator:
+ *   parity = 0: even number of ones in accumulator
+ *   parity = 1: odd  number of ones in accumulator
+ */
+void
+psw_compute_parity_bit(void)
 {
-	return memory_read8(INT_MEM_ID, _PSW_) >> 7;
+	int parity = 0;
+	uint8_t acc = memory_read8(INT_MEM_ID, _ACC_);
+
+	while (acc) {
+		parity = !parity;
+		acc = acc & (acc - 1);
+	}
+
+	psw_write_bit(PSW_BIT_P, parity);
 }