P89V51RD2 Philips Semiconductors, P89V51RD2 Datasheet - Page 59

• Manufacturer Part Number: P89V51RD2
• Description: 8-bit 80C51 5 V low power 64 kB Flash microcontroller with 1 kB RAM
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 12964
Product data
Fig 28. Oscillator characteristics.
Using the on-chip oscillator
C 2
C 1
7.12.2 Clock doubling option
XTAL2
XTAL1
V SS
By default, the device runs at 12 clocks per machine cycle (x1 mode). The device has
a clock doubling option to speed up to 6 clocks per machine cycle (please see
Table
using IAP. When set, the EDC bit in FST register will indicate 6 clock mode.
The clock double mode is only for doubling the internal system clock and the internal
flash memory, i.e. EA = 1. To access the external memory and the peripheral devices,
careful consideration must be taken. Also note that the crystal output (XTAL2) will not
be doubled.
Table 58:
Table 59:
Not Bit addressable; Reset value: xxxxx0xxB
Table 60:
Device
P89V51RD2
Bit
7
6
5 to 4
3
2 to 0
Bit
Symbol
58). Clock double mode can be enabled either by an external programmer or
Clock doubling features
FST - Flash status register (address B6) bit allocation
FST - Flash status register (address B6) bit description
Symbol
-
SB
-
EDC
-
7
-
002aaa543
Standard mode (x1)
Clocks per
machine cycle
12
Rev. 01 — 01 March 2004
SB
6
Description
Reserved for future use. Should be set to ‘0’ by user programs.
Security bit.
Reserved for future use. Should be set to ‘0’ by user programs.
Enable double clock.
Reserved for future use. Should be set to ‘0’ by user programs.
5
-
External clock drive
Max. external
clock frequency
(MHz)
40
4
-
8-bit microcontrollers with 80C51 core
oscillator
external
signal
EDC
NC
3
Clock double mode (x2)
Clocks per
machine cycle
6
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P89V51RD2
2
-
002aaa546
XTAL2
XTAL1
V SS
Max. external
clock frequency
(MHz)
20
1
-
59 of 75
0
-