- Fix: got BBSY too early

"After receiving the negation of BBSY, SSYN and BGn, the requesting device
asserts BBSY"
- Fixed arbitration for emalated CPU.

10.01_base/2_src/pru1/pru1_main_unibus.c

@@ -150,6 +150,7 @@ void main(void) {
 					cpu_grant_mask = sm_arb_worker_cpu(); // GRANT device requests
 					// do not read GRANT signals from UNIBUS, BG/NPGOUT not visible for
 					// emulated devices
+//					sm_arb.device_forwarded_grant_mask = 0 ;
 				} else {
 					// device requests GRANTed by physical CPU
 
@@ -291,7 +292,10 @@ void main(void) {
 				break;
 			case ARM2PRU_CPU_ENABLE:
 				// bool flag much faster to access than shared mailbox member.
-				emulate_cpu = mailbox.cpu_enable;
+				if (emulate_cpu != mailbox.cpu_enable) {
+					emulate_cpu = mailbox.cpu_enable;
+					sm_arb_reset() ; // new arbitration algorithms
+				}
 				mailbox.arm2pru_req = ARM2PRU_NONE; // ACK: done
 				break;
 			case ARM2PRU_BUSLATCH_SET: { // set a mux register

10.01_base/2_src/pru1/pru1_statemachine_arbitration.c

@@ -103,7 +103,7 @@ void sm_arb_reset() {
 	sm_arb.device_forwarded_grant_mask = 0;
 	sm_arb.device_request_signalled_mask = 0;
 
-	sm_arb.bbsy_wait_grant_mask = 0;
+	sm_arb.grant_bbsy_ssyn_wait_grant_mask = 0;
 	sm_arb.cpu_request = 0;
 	sm_arb.arbitrator_grant_mask = 0;
 	timeout_cleanup(TIMEOUT_SACK);
@@ -139,7 +139,9 @@ uint8_t sm_arb_worker_none(uint8_t grant_mask) {
  "Wait for BBSY clear" may not be part of the arbitration protocol.
  But it guarantees caller may now issue an DMA or INTR.
 
- grant_mask: state of all BGIN/NPGIN lines
+ grant_mask: state of all BGIN/NPGIN lines, 
+ as forwarded by other devices from physical CPU
+ or generated directly by emulated CPU
  */
 uint8_t sm_arb_worker_device(uint8_t grant_mask) {
 	if (sm_arb.cpu_request) {
@@ -178,10 +180,10 @@ uint8_t sm_arb_worker_device(uint8_t grant_mask) {
 	sm_arb.device_request_signalled_mask = sm_arb.device_request_mask;
 
 	// read GRANT IN lines from CPU (Arbitrator). 
-	// Only one nit ion cpu_grant_mask at a time may be active, else arbitrator malfunction.
+	// Only one bit on cpu_grant_mask at a time may be active, else arbitrator malfunction.
 	// Arbitrator asserts SACK is inactive
 
-	if (sm_arb.bbsy_wait_grant_mask == 0) {
+	if (sm_arb.grant_bbsy_ssyn_wait_grant_mask == 0) {
 		// State 1: Wait For GRANT:
 		// process the requested grant for an open requests.
 		// "A device may not accept a grant (assert SACK) after it passes the grant"
@@ -201,16 +203,23 @@ uint8_t sm_arb_worker_device(uint8_t grant_mask) {
 			// -> DMA and INTR statemachine must wait for BBSY.
 
 			// Arbitrator should remove GRANT now. Data section on Bus still BBSY
-			sm_arb.bbsy_wait_grant_mask = grant_mask;	// next is State 2: wait for BBSY clear
+			sm_arb.grant_bbsy_ssyn_wait_grant_mask = grant_mask;
+			// next is State 2: wait for BBSY clear
 		}
-		return 0; // no GRANT for us, or wait for BBSY
+		return 0; // no REQUEST, or no GRANT for us, or wait for BG/BPG & BBSY && SSYN
 	} else {
-		// State 2: wait for BBSY to clear
+		// State 2: wait for BG/NPG, BBSY and SSYN to clear
+		// DMA and INTR:
+		// "After receiving the negation of BBSY, SSYN and BGn,
+		// the requesting device asserts BBSY"
+		if (grant_mask & sm_arb.grant_bbsy_ssyn_wait_grant_mask)
+			return 0; // BG*/NPG still set
 		if (buslatches_getbyte(1) & BIT(6))
 			return 0; // BBSY still set
-		grant_mask = sm_arb.bbsy_wait_grant_mask;
-		sm_arb.bbsy_wait_grant_mask = 0; // Next State is 1
-
+		if (buslatches_getbyte(4) & BIT(5))
+			return 0; // SSYN still set
+		grant_mask = sm_arb.grant_bbsy_ssyn_wait_grant_mask;
+		sm_arb.grant_bbsy_ssyn_wait_grant_mask = 0; // Next State is 1
 		return grant_mask; // signal what request we got granted.
 	}
 }

10.01_base/2_src/pru1/pru1_statemachine_arbitration.h

@@ -53,7 +53,7 @@ typedef struct {
 	// for BBSY clear. 
 	// 0: not waitong for BBSY.
 	// != saves GRANTed request and indicates BBSY wait state
-	uint8_t bbsy_wait_grant_mask;
+	uint8_t grant_bbsy_ssyn_wait_grant_mask;
 
 	/*** master ****/
 	// CPU is requesting memory access via PRU2ARM_DMA/mailbox.dma