W79E548 Datasheet, PDF (28/79 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E548/W79L548
Accumulator
Bit:
7
6
5
4
3
2
1
0
ACC.7 ACC.6 ACC.5 ACC.4 ACC.3 ACC.2 ACC.1 ACC.0
Mnemonic: ACC
Address: E0h
ACC.7-0: The A (or ACC) register is the standard 8052 accumulator.
Extended Interrupt Enable
Bit:
7
6
5
4
3
2
1
0
-
-
-
EWDI
-
-
-
-
Mnemonic: EIE
Address: E8h
EIE.7-5: Reserved bits, will read high
EWDI: Enable Watchdog timer interrupt
B Register
Bit:
7
6
5
4
3
2
1
0
B.7
B.6
B.5
B.4
B.3
B.2
B.1
B.0
Mnemonic: B
Address: F0h
B.7-0: The B register is the standard 8052 register that serves as a second accumulator.
Extended Interrupt Priority
Bit:
7
6
5
4
3
2
1
0
-
-
-
PWDI
-
-
-
-
Mnemonic: EIP
Address: F8h
EIP.7-5: Reserved bits.
PWDI: Watchdog timer interrupt priority.
8. INSTRUCTION
The W79E(L)548 executes all the instructions of the standard 8032 family. The operation of these
instructions, their effect on the flag bits and the status bits is exactly the same. However, timing of
these instructions is different. The reason for this is two fold. Firstly, in the W79E(L)548, each machine
cycle consists of 4 clock periods, while in the standard 8032 it consists of 12 clock periods. Also, in the
W79E(L)548 there is only one fetch per machine cycle i.e. 4 clocks per fetch, while in the standard
8032 there can be two fetches per machine cycle, which works out to 6 clocks per fetch.
The advantage the W79E(L)548 has is that since there is only one fetch per machine cycle, the
number of machine cycles in most cases is equal to the number of operands that the instruction has.
In case of jumps and calls there will be an additional cycle that will be needed to calculate the new
address. But overall the W79E(L)548 reduces the number of dummy fetches and wasted cycles,
thereby improving efficiency as compared to the standard 8032.
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