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DS87C550 High-Speed Microcontroller User’s Guide Supplement
16 of 93
Timer 0, 1, and 2 values as a function of various clock control settings
OSC CYCLES
PER TIMER 0/1/2
CLOCK.
OSC CYCLES PER
SERIAL PORT CLK,
MODE 0
OSC CYCLES PER
SERIAL PORT CLK,
MODE 2
CD1:0 4X/ 2X
OSCILLATOR
CYCLES PER
MACHINE.
CYCLE
TxM=0
TxM=1
OSC CYCLES
PER TIMER 2
CLK, BAUD
RATE GEN.
SM2=0
SM2=1
SMOD=0
SMOD=1
00
1
1
12
1
2
3
1
64
32
00
0
2
12
2
2
6
2
64
32
01
x
Reserved
10
x
4
12
4
2
12
4
64
32
11
x
1024
3072
1024
512
3072
1024
64
32
MD2, MD1, MD0
Bits 2-0
Stretch MOVX Select 2-0.
These bits select the time by which external MOVX
cycles are to be stretched. This allows slower memory or peripherals to be
accessed without using ports or manual software intervention. The
RD
or
WR
strobe will be stretched by the specified interval, which will be transparent to
the software except for the increased time to execute to MOVX instruction. All
internal MOVX instructions on devices containing MOVX SRAM are performed
at the 2 machine cycle rate.
MD2
MD1
MD0
Stretch Value
MOVX Duration
0
0
0
0
2 Machine Cycles
0
0
1
1
3 Machine Cycles (reset default)
0
1
0
2
4 Machine Cycles
0
1
1
3
5 Machine Cycles
1
0
0
4
9 Machine Cycles
1
0
1
5
10 Machine Cycles
1
1
0
6
11 Machine Cycles
1
1
1
7
12 Machine Cycles