EF9345 Datasheet, PDF (11/38 Pages) STMicroelectronics – HMOS2 SINGLE CHIP SEMI-GRAPHIC DISPLAY PROCESSOR

EF9345
MEMORY ORGANIZATION
Logical And Physical Addressing
The physical 16-Kbyte addressingspace is logicaly
partitioned by EF9345 into 40-byte buffers (Fig-
ure 8). More precisely, a logical address is given by
an X, Y, Z triplet where :
- X = (0 to 39) points to a byte inside a buffer,
- Y = (0, 1 ; 8 to 31) points to a buffer inside a
1 Kbyte blocks,
- Z = (0 to 15) points to a block.
Obviously, 1 K = 2¹⁰ = 1024 cannot be exactly
divided by 40. Consequently, any block holds 25
full buffers and a 24-byte remainder. Provided that
the physical memory is a multiple of 2 Kbytes, the
remainders are paired in such a way as to make
available :
- A full buffer (Y = 1) in each even block,
- A partial buffer (Y = 1 ; X = 32 to 39) in each odd
block.
Figure 8 : Memory Row Buffer
X
8
32 39
X
8
32 39
DISTRICT
0
1
8
31
0
1
8
Y
31
0
1
8
BLOCK 0
(1Kbyte)
BLOCK 1
BLOCK 2
31
0
Y
1
8
BLOCK 3
31
0
9
DISTRICT
DISTRICT
120-BYTE ROW BUFFER
80-BYTE ROW BUFFER
Notes : - Row buffers lay indide a district
- At two or three successive block addresses (modulo 4)
- First block address is even
Pointers
Each X, Y and Z component of a logical address is
binary encoded and packed in two 8-bits registers.
Such a register pair is a pointer (Figure 9). EF9345
contains two pointers :
- R4, R5 : auxiliary pointer,
- R6, R7 : main pointer.
R5 and R7 have the same format. Each one holds
an X component and the two LSB’s of a Z compo-
nent. This packing induces a partitioning of Z in 4
districts of 4 blocks each.
R5, R7 points to a block number in a district. R4
and R6 have a slightly different format : Each one
holds a Y component and the LSB of the district
number. But R6 holds both district MSB
Figure 11 gives the logical to physical address
transcoding scheme performed on chip.
Figure 9 : Pointer Auto Incrementation
d1 d’1 d0
b0 b1 5
Y = (0, 1 ; 8 to 31)
43210
X = 0 to 39
43210
R6
MAIN
POINTER
R7
_ _ _d’0
b’0 b’1 5
Y’ = (0, 1 ; 8 to 31)
43210
X’ = 0 to 39
43210
R4
AUXILIARY
POINTER
R5
0
39
0
2=0
4=0
6=0
8
1
1
3= 1
5= 1
7= 1
9
Z = (0 to 15)
3210
D
B
1
X
31
Y
10 0
B
2
2
X incrementation
Modulo 40
Y incrementation
Modulo 24
3
Z incrementation/
decrementation
Modulo 4 on the
block number only
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