new command: memsize. new function z80_memsize_detect().

1 files changed, 33 insertions, 0 deletions

diff --git a/avr/z80-if.c b/avr/z80-if.c
index 6183849..6d83172 100644
--- a/avr/z80-if.c
+++ b/avr/z80-if.c
@@ -463,6 +463,39 @@ void z80_setaddress(uint32_t addr)
 	PIN_ADB = (((addr >> 16) << ADB_SHIFT) ^ P_ADB) & MASK(ADB_WIDTH) << ADB_SHIFT;
 }
 
+int32_t z80_memsize_detect(void)
+{
+	const uint8_t PATTERN_1	= 0x55;
+	const uint8_t PATTERN_2	= ~PATTERN_1;
+	uint32_t addr;
+
+	if (!(z80_bus_cmd(Request) & ZST_ACQUIRED))
+		return  -EBUSTO;
+
+	uint8_t ram_0 = z80_read(0);
+	uint8_t ram_1 = z80_read(1);
+
+	z80_write(0, ram_0 ^ 0xff);
+	z80_write(1, ram_1);
+	if ((z80_read(0) ^ ram_0) != 0xff) {
+		addr = 0;
+	} else {
+		z80_write(0, PATTERN_1);
+		for (addr=1; addr < CONFIG_SYS_RAMSIZE_MAX; addr <<= 1) {
+			uint8_t ram_i = z80_read(addr);
+			z80_write(addr, PATTERN_2);
+			if (z80_read(0) != PATTERN_1 || z80_read(addr) != PATTERN_2)
+				break;
+			z80_write(addr, ram_i);
+		}
+	}
+
+	z80_write(0, ram_0);
+	z80_bus_cmd(Release);
+
+	return addr;
+}
+
 void z80_write(uint32_t addr, uint8_t data)
 {
 	z80_setaddress(addr);