w77e58 Winbond Electronics Corp America, w77e58 Datasheet - Page 41

• Manufacturer Part Number: w77e58
• Description: 8 Bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

Machine cycles in standard 8032 = 10 + (26 * CNT)
Machine cycles in W77E58 = 10 + (26 * CNT)
If CNT = 50
Clock cycles in standard 8032= ((10 + (26 *50)) * 12 = (10 + 1300) * 12 = 15720
Clock cycles in W77E58 = ((10 + (26 * 50)) * 4 = (10 + 1300) * 4 = 5240
Block Move with Two Data Pointers in W77E58:
; SH and SL are the high and low bytes of Source Address
; DH and DL are the high and low bytes of Destination Address
; CNT is the number of bytes to be moved
MOV
MOV
MOV
INC
MOV
LOOP:
MOVX A, @DPTR
INC
DEC
MOVX @DPTR, A
INC
INC
DJNZ R2, LOOP
Machine cycles in W77E58 = 12 + (15 * CNT)
If CNT = 50
Clock cycles in W77E58 = (12 + (15 * 50)) * 4 = (12 + 750) * 4 = 3048
We can see that in the first program the standard 8032 takes 15720 cycles, while the W77E58 takes
only 5240 cycles for the same code. In the second program, written for the W77E58, program
execution requires only 3048 clock cycles. If the size of the block is increased then the saving is even
greater.
External Data Memory Access Timing:
The timing for the MOVX instruction is another feature of the W77E58. In the standard 8032, the
MOVX instruction has a fixed execution time of 2 machine cycles. However in the W77E58, 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
W77E58 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
R2, #CNT
DPS, #00h
DPTR, #DHDL ; Load DPTR with Destination address
DPS
DPTR, #SHSL ; Load DPTR1 with Source address
DPTR
DPS
DPTR
DPS
; Load R2 with the count value
; Clear DPS to point to DPTR
; Set DPS to point to DPTR1
; Get data from Source block
; Increment source address
; Clear DPS to point to DPTR
; Write data to Destination
; Increment destination address
; Set DPS to point to DPTR1
; Check if all done
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Machine cycles of W77E58
Preliminary W77E58
Publication Release Date: March 1999
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Revision A1