W77C32_07 Datasheet, PDF (38/78 Pages) Winbond – 8-BIT MICROCONTROLLER

W77C32/W77C032A
Machine cycles in W77C032 = 12 + (15 * CNT)
If CNT = 50
Clock cycles in W77C032 = (12 + (15 * 50)) * 4 = (12 + 750) * 4 = 3048
We can see that in the first program the standard 8032 takes 15720 cycles, while the W77C032 takes
only 5240 cycles for the same code. In the second program, written for the W77C032, program
execution requires only 3048 clock cycles. If the size of the block is increased then the saving is even
greater.
8.3 External Data Memory Access Timing
The timing for the MOVX instruction is another feature of the W77C032. In the standard 8032, the
MOVX instruction has a fixed execution time of 2 machine cycles. However in the W77C032, the
duration of the access can be varied by the user.
The instruction starts off as a normal op-code fetch of 4 clocks. In the next machine cycle, the
W77C032 puts out the address of the external Data Memory and the actual access occurs here. The
user can change the duration of this access time by setting the STRETCH value. The Clock Control
SFR (CKCON) has three bits that control the stretch value. These three bits are M2-0 (bits 2-0 of
CKCON). These three bits give the user 8 different access time options. The stretch can be varied
from 0 to 7, resulting in MOVX instructions that last from 2 to 9 machine cycles in length. Note that the
stretching of the instruction only results in the elongation of the MOVX instruction, as if the state of the
CPU was held for the desired period. There is no effect on any other instruction or its timing. By
default, the Stretch value is set at 1, giving a MOVX instruction of 3 machine cycles. If desired by the
user the stretch value can be set to 0 to give the fastest MOVX instruction of only 2 machine cycles.
Table 4. Data Memory Cycle Stretch Values
M2
M1
M0
MACHINE
RD OR WR
CYCLES ^{STROBE WIDTH IN}
RD OR WR
STROBE WIDTH
CLOCKS
@25 MHZ
0
0
0
2
2
80 nS
0
0
1 3 (default)
4
160 nS
0
1
0
4
8
320 nS
0
1
1
5
12
480 nS
1
0
0
6
16
640 nS
1
0
1
7
20
800 nS
1
1
0
8
24
960 nS
1
1
1
9
28
1120 nS
RD OR WR
STROBE WIDTH
@40 MHZ
50 nS
100 nS
200 nS
300 nS
400 nS
500 nS
600 nS
700 nS
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