diff --git a/backend_hiti.c b/backend_hiti.c
index 227d24a..afcbda0 100644
--- a/backend_hiti.c
+++ b/backend_hiti.c
@@ -134,7 +134,7 @@ struct hiti_cmd {
 #define CMD_ESD_C_SHPTC  0x830C /* CS Send Heating Parameters & Tone Curve XX (n arg) */
 
 /* Extended Flash/NVram */
-#define CMD_EFM_RNV    0x8405 /* Read NVRam (1 arg) -- arg is offset, 1 byte resp of data @ that offset. -- All newer than P51x */
+#define CMD_EFM_RNV    0x8405 /* Read NVRam (1 arg) -- arg is offset, 1 byte resp of data @ that offset. -- P51x */
 #define CMD_EFM_RD     0x8408 /* Read single location (2 byte offset arg, 1 byte of data @ that offset -- not P51x */
 #define CMD_EFM_SHA    0x840E /* Set Highlight Adjustment (5 arg) -- XXX RE */
 
@@ -376,7 +376,7 @@ struct hiti_matrix {
 	uint8_t row9[12]; // all 00 except last, which is 0xa5
 
 /*@a0*/	uint16_t errorcount[31];
-	uint8_t unk_rowd[2]; // seems to be 00 cc ?
+	uint8_t rowd[2]; // seems to be 00 cc ?
 
 /*@e0*/	uint16_t tpc_4x6;
 	uint16_t tpc_5x7;
@@ -392,9 +392,28 @@ struct hiti_matrix {
 	uint8_t tphv_a;
 	uint8_t tphv_d;
 	uint8_t unk_rowf2[2]; // all 00
-/* @100 */
+
+/*@100*/uint8_t unk_row10[16];
+/*@110*/uint8_t unk_row11[16];
+/*@120*/uint8_t unk_row12[16];
+/*@130*/uint8_t unk_row13[16];
+/*@140*/uint8_t unk_row14[16];
+/*@150*/uint8_t unk_row15[16];
+/*@160*/uint8_t unk_row16[16];
+/*@170*/uint8_t unk_row17[16];
+/*@180*/uint8_t unk_row18[16];
+/*@190*/uint8_t unk_row19[16];
+/*@1a0*/uint8_t unk_row1a[16];
+/*@1b0*/uint8_t unk_row1b[16];
+/*@1c0*/uint8_t unk_row1c[16];
+/*@1d0*/uint8_t unk_row1d[16];
+/*@1e0*/uint8_t unk_row1e[16];
+/*@1f0*/uint8_t unk_row1f[16];
+/*@200*/
 } __attribute__((packed));
 
+STATIC_ASSERT(sizeof(struct hiti_matrix) == 512);
+
 struct hiti_ribbon {
 	uint16_t unk;
 	uint8_t type;  /* RIBBON_TYPE_XXX */
@@ -440,7 +459,7 @@ struct hiti_ctx {
 	struct marker marker;
 	char     version[256];
 	char     id[256];
-	uint8_t  matrix[256];  // XXX convert to struct matrix */
+	uint8_t  matrix[512];  // XXX convert to struct matrix */
 	struct hiti_ribbon ribbon;
 	struct hiti_paper  paper;
 	struct hiti_calibration calibration;
@@ -900,7 +919,7 @@ static int hiti_get_info(struct hiti_ctx *ctx)
 	{
 		int i;
 		DEBUG("MAT ");
-		for (i = 0 ; i < 256 ; i++) {
+		for (i = 0 ; i < 512 ; i++) {
 			if (i != 0 && (i % 16 == 0)) {
 				DEBUG2("\n");
 				DEBUG("    ");
@@ -2559,7 +2578,7 @@ static int hiti_query_matrix(struct hiti_ctx *ctx)
 	int i;
 	uint16_t len = 1;
 
-	for (i = 0 ; i < 256 ; i++) {
+	for (i = 0 ; i < 512 ; i++) {
 		uint16_t offset = cpu_to_be16(i);
 
 		ret = hiti_docmd_resp(ctx, CMD_EFM_RD, (uint8_t*)&offset, sizeof(offset), &ctx->matrix[i], &len);
@@ -2576,14 +2595,30 @@ static int hiti_query_matrix_51x(struct hiti_ctx *ctx)
 	int i;
 	uint16_t len = 1;
 
-	for (i = 0 ; i < 256 ; i++) {
-		uint8_t offset = i;
+	uint8_t lun = 0;
+	ret = hiti_docmd(ctx, CMD_PCC_STP, (uint8_t*)&lun, sizeof(lun), &len);
+	if (ret)
+		return ret;
 
+	for (i = 0 ; i < 512 ; i++) {
+		uint8_t offset = i % 256;
+		if (i == 256) {
+			lun = 1;
+			ret = hiti_docmd(ctx, CMD_PCC_STP, (uint8_t*)&lun, sizeof(lun), &len);
+			if (ret)
+				return ret;
+		}
 		ret = hiti_docmd_resp(ctx, CMD_EFM_RNV, (uint8_t*)&offset, sizeof(offset), &ctx->matrix[i], &len);
 		if (ret)
 			return ret;
 	}
 
+	lun = 0;
+	ret = hiti_docmd(ctx, CMD_PCC_STP, (uint8_t*)&lun, sizeof(lun), &len);
+	if (ret)
+		return ret;
+
+
 	return CUPS_BACKEND_OK;
 }