Maxim Integrated DS80C390 - Manual (Page 8)

DS80C390
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required the same amount of time: two machine cycles or 24 oscillator cycles. In the DS80C390, the
MOVX instruction takes as little as two machine cycles or 8 oscillator cycles but the “MOV direct,
direct” uses three machine cycles or 12 oscillator cycles. While both are faster than their original
counterparts, they now have different execution times. This is because the device usually uses one
instruction cycle for each instruction byte. Examine the timing of each instruction for familiarity with the
changes. Note that a machine cycle now requires just 4 clocks, and provides one ALE pulse per cycle.
Many instructions require only one cycle, but some require five. Refer to the user’s guide for details and
individual instruction timing.
SPECIAL FUNCTION REGISTERS
Special Function Registers (SFRs) control most special features of the microcontroller. This allows the
device to have many new features but use the same instruction set as the 8051. When writing software to
use a new feature, an equate statement defines the SFR to an assembler or compiler. This is the only
change needed to access the new function. The DS80C390 duplicates the SFRs contained in the standard
80C52. Table 2 shows the register addresses and bit locations. Many are standard 80C52 registers. The
user’s guide contains a full description of all SFRs.
SPECIAL FUNCTION REGISTER LOCATION Table 2
Register Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 ADDRESS
P4 P4.7 P4.6 P4.5 P4.4 P4.3 P4.2 P4.1 P4.0 80h
SP 81h
DPL 82h
DPH 83h
DPL1 84h
DPH1 85h
DPS ID1 ID0 TSL - - - - SEL 86h
PCON SMOD_0 SMOD0 OFDF OFDE GF1 GF0 STOP IDLE 87h
TCON TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 88h
TMOD GATE
C/ T
M1 M0 GATE
C/ T
M1 M0 89h
TL0 8Ah
TL1 8Bh
TH0 8Ch
TH1 8Dh
CKCON WD1 WD0 T2M T1M T0M MD2 MD1 MD0 8Eh
P1 INT5/P1.7 INT4/P1.6 INT3/P1.5 INT2/P1.4 TXD1/P1.3 RXD1/P1.2 T2EX/P1.1 T2/P1.0 90h
EXIF IE5 IE4 IE3 IE2 CKRY RGMD RGSL BGS 91h
P4CNT - SBCAN P4CNT.5 P4CNT.4 P4CNT.3 P4CNT.2 P4CNT.1 P4CNT.0 92h
DPX 93h
DPX1 95h
C0RMS0 96h
C0RMS1 97h
SCON0 SM0/FE_0 SM1_0 SM2_0 REN_0 TB8_0 RB8_0 TI_0 RI_0 98h
SBUF0 99h
ESP - - - - - - ESP.1 ESP.0 9Bh
AP 9Ch
ACON - - - - - SA AM1 AM0 9Dh
C0TMA0 9Eh
C0TMA1 9Fh
P2 P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0 A0h
P5 P5.7 P5.6 P5.5 P5.4 P5.3 P5.2 P5.1 P5.0 A1h
P5CNT CAN1BA CAN0BA SP1EC C1_I/O C0_I/O P5CNT.2 P5CNT.1 P5CNT.0 A2h
C0C ERIE STIE PDE SIESTA CRST AUTOB ERCS SWINT A3h
C0S BSS EC96/128 WKS RXS TXS ER2 ER1 ER0 A4h