W79E548 Datasheet, PDF (15/79 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E548/W79L548
Clock Control
Bit:
7
WD1
6
WD0
Mnemonic: CKCON
5
T2M
4
T1M
3
T0M
2
MD2
1
MD1
Address: 8Eh
0
MD0
WD1−0: Watchdog timer mode select bits: These bits determine the time-out period for the watchdog
timer. In all four time-out options the reset time-out is 512 clocks more than the interrupt time-
out period.
WD1
0
0
1
1
WD0
0
1
0
1
INTERRUPT TIME-OUT
2¹⁷
2²⁰
2²³
2²⁶
RESET TIME-OUT
2¹⁷ + 512
2²⁰ + 512
2²³ + 512
2²⁶ + 512
T2M: Timer 2 clock select: When T2M is set to 1, timer 2 uses a divide by 4 clock, and when set to
0 it uses a divide by 12 clock.
T1M: Timer 1 clock select: When T1M is set to 1, timer 1 uses a divide by 4 clock, and when set to
0 it uses a divide by 12 clock.
T0M: Timer 0 clock select: When T0M is set to 1, timer 0 uses a divide by 4 clock, and when set to
0 it uses a divide by 12 clock.
MD2−0: Stretch MOVX select bits: These three bits are used to select the stretch value for the MOVX
instruction. Using a variable MOVX length enables the user to access slower external
memory devices or peripherals without the need for external circuits. The RD or WR strobe
will be stretched by the selected interval. When accessing the on-chip SRAM, the MOVX
instruction is always in 2 machine cycles regardless of the stretch setting. By default, the
stretch has value of 1. If the user needs faster accessing, then a stretch value of 0 should be
selected.
MD2 MD1 MD0 Stretch value MOVX duration
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
0
2 machine cycles
1
3 machine cycles (Default)
2
4 machine cycles
3
5 machine cycles
4
6 machine cycles
5
7 machine cycles
6
8 machine cycles
7
9 machine cycles
- 15 -
Publication Release Date: December 12, 2005
Revision A1