diff --git a/arch/z80/sms/Makefile b/arch/z80/sms/Makefile
index 1f4b9ae..a9c3a23 100644
--- a/arch/z80/sms/Makefile
+++ b/arch/z80/sms/Makefile
@@ -15,7 +15,7 @@ $(SMSROM):
 $(BLKPACK):
 	$(MAKE) -C ../tools
 
-blkfs: $(BLKPACK)
+blkfs: $(BLKPACK) $(BASE)/blk.fs blk.fs
 	cat $(BASE)/blk.fs blk.fs | $(BLKPACK) > $@
 
 $(STAGE):
diff --git a/arch/z80/sms/blk.fs b/arch/z80/sms/blk.fs
index 516435a..b3e295f 100644
--- a/arch/z80/sms/blk.fs
+++ b/arch/z80/sms/blk.fs
@@ -27,9 +27,9 @@ always stay zero. )
 : _sfont ( a -- Send font to VDP )
     7 0 DO C@+ _data 3 _zero LOOP DROP
     ( blank row ) 4 _zero ;
-: CELL! ( tilenum pos )
-    2 * 0x7800 OR _ctl ( tilenum )
-    0x5e MOD _data 1 _zero ;
+: CELL! ( c pos )
+    2 * 0x7800 OR _ctl ( c )
+    0x20 - ( glyph ) 0x5e MOD _data 0 _data ;
 ( ----- 604 )
 : VDP$
     9 0 DO _idat I 2 * + @ _ctl LOOP _blank
diff --git a/arch/z80/ti84/Makefile b/arch/z80/ti84/Makefile
index 50b5a7e..599df30 100644
--- a/arch/z80/ti84/Makefile
+++ b/arch/z80/ti84/Makefile
@@ -15,7 +15,7 @@ $(TARGET): xcomp.fs $(STAGE) blkfs
 $(BLKPACK):
 	$(MAKE) -C ../tools
 
-blkfs: $(BLKPACK)
+blkfs: $(BLKPACK) $(BASE)/blk.fs blk.fs
 	cat $(BASE)/blk.fs blk.fs | $(BLKPACK) > $@
 
 $(STAGE):
diff --git a/arch/z80/ti84/blk.fs b/arch/z80/ti84/blk.fs
index 061f78f..9fd1d78 100644
--- a/arch/z80/ti84/blk.fs
+++ b/arch/z80/ti84/blk.fs
@@ -110,9 +110,9 @@ CODE _wait
 ( ----- 609 )
 : _atrow! ( pos -- ) COLS / FNTH 1+ * _row! ;
 : _tocol ( pos -- col off ) COLS MOD FNTW 1+ * 8 /MOD ;
-: CELL! ( g pos -- )
-    DUP _atrow! DUP _tocol _col! ROT ( pos coff g )
-    FNTH * ~FNT + ( pos coff a )
+: CELL! ( c pos -- )
+    DUP _atrow! DUP _tocol _col! ROT ( pos coff c )
+    0x20 - FNTH * ~FNT + ( pos coff a )
     _xinc _data@ DROP
     FNTH 0 DO ( pos coff a )
         C@+ 2 PICK 8 -^ LSHIFT
diff --git a/blk.fs b/blk.fs
index 9b94928..7787f46 100644
--- a/blk.fs
+++ b/blk.fs
@@ -2218,7 +2218,7 @@ Load range: B402-B403
 : XYPOS! COLS LINES * MOD DUP CURSOR! XYPOS ! ;
 : AT-XY ( x y -- ) COLS * + XYPOS! ;
 '? NEWLN NIP NOT [IF]
-: NEWLN ( ln -- ) COLS * DUP COLS + SWAP DO 0 I CELL! LOOP ;
+: NEWLN ( ln -- ) COLS * DUP COLS + SWAP DO 0x20 I CELL! LOOP ;
 [THEN]
 : _lf XYMODE C@ IF EXIT THEN
     XYPOS @ COLS / 1+ LINES MOD DUP NEWLN
@@ -2228,7 +2228,7 @@ Load range: B402-B403
 : (emit)
     DUP 0x08 = IF DROP _bs EXIT THEN
     DUP 0x0d = IF DROP _lf EXIT THEN
-    0x20 - DUP 0< IF DROP EXIT THEN
+    DUP 0x20 < IF DROP EXIT THEN
     XYPOS @ CELL!
     XYPOS @ 1+ DUP COLS MOD IF XYPOS! ELSE _lf THEN ;
 : GRID$ 0 XYPOS! 0 XYMODE C! ;
@@ -2795,15 +2795,15 @@ them.  We insert a blank one at the end of those 7. )
 : _sfont ( a -- Send font to TMS )
     7 0 DO C@+ _data LOOP DROP
     ( blank row ) 0 _data ;
-: CELL! ( tilenum pos )
+: CELL! ( c pos )
     0x7800 OR _ctl ( tilenum )
-    0x5e MOD _data ;
+    0x20 - ( glyph ) 0x5e MOD _data ;
 : COLS 40 ; : LINES 24 ;
 : TMS$
     0x8100 _ctl ( blank screen ) _blank
     0x4000 _ctl 0x5e 0 DO ~FNT I 7 * + _sfont LOOP
     0x820e _ctl ( name table 0x3800 )
-    0x8400 _ctl ( patter table 0x0000 )
+    0x8400 _ctl ( pattern table 0x0000 )
     0x87f0 _ctl ( colors 0 and 1 )
     0x8000 _ctl 0x81d0 _ctl ( text mode, display on ) ;
 ( ----- 520 )
diff --git a/cvm/forth.fs b/cvm/forth.fs
index ad37562..52b0ec2 100644
--- a/cvm/forth.fs
+++ b/cvm/forth.fs
@@ -1,6 +1,6 @@
 : COLS 80 ; : LINES 32 ;
 : CURSOR! ( pos -- ) COLS /MOD 6 PC! ( y ) 5 PC! ( x ) ;
-: CELL! ( g pos -- ) CURSOR! 0x20 + 0 PC! ;
+: CELL! ( c pos -- ) CURSOR! 0 PC! ;
 : NEWLN ( ln -- ) DROP 0xa 0 PC! ;
 
 SYSVARS 0x70 + CONSTANT GRID_MEM
diff --git a/doc/protocol.txt b/doc/protocol.txt
index e92d6f4..1da55ac 100644
--- a/doc/protocol.txt
+++ b/doc/protocol.txt
@@ -44,7 +44,7 @@ allows random access to it.
 
 COLS      -- n     Number of columns in the device
 LINES     -- n     Number of lines in the device
-CELL!     g pos -- Set glyph at pos
+CELL!     c pos -- Set character at pos
 
 Optional:
 NEWLN     ln --    "Enter" line ln
@@ -53,10 +53,10 @@ CURSOR!   pos --   Set cursor's position
 "pos" is a simple number (y * cols) + x. For example, if we
 have 40 columns per line, the position (x, y) (12, 10) is 412.
 
-A glyph is ASCII-0x20. If the resulting glyph number exceeds the
-number of glyphs in the font, it's up to CELL! to ignore it.
-
-Glyph 0 is always blank.
+CELL! is not expected to be called with an out-of-range char-
+acter. For example, glyphs are often mapped starting at 0x20
+(space). On most systems, CELL! should not be called with c <
+0x20.If it is, CELL! should do nothing.
 
 NEWLN is called when we "enter" a new line, that is, when we
 overflow from previous line or when 0x0d ( ASCII CR ) is emit-