Rainbow-electronics T89C51CC01 Uživatelský manuál stáhnout pdf (Strana 19)

19

T89C51CC01

Rev. D – 17-Dec-01

Figure 6. Mode Switching Waveforms

Note: In order to prevent any incorrect operation while operating in the X2 mode, users must be

aware that all peripherals using the clock frequency as a time reference (UART, timers...)

will have their time reference divided by two. For example a free running timer generating

an interrupt every 20 ms will then generate an interrupt every 10 ms. A UART with a

4800 baud rate will have a 9600 baud rate.

6.2 Register Table 12. CKCON Register

CKCON (S:8Fh)

Clock Control Register

XTAL2

XTAL1

CPU

X2 bit

X2STD STD

76543210

CANX2 WDX2 PCAX2 SIX2 T2X2 T1X2 T0X2 X2

Bit

Number

Bit

Mnemonic Description

7CANX2

CAN clock (1)

Clear to select 6 clock periods per peripheral clock cycle.

Set to select 12 clock periods per peripheral clock cycle.

6WDX2

Watchdog clock (1)

Clear to select 6 clock periods per peripheral clock cycle.

Set to select 12 clock periods per peripheral clock cycle.

5 PCAX2

Programmable Counter Array clock (1)

Clear to select 6 clock periods per peripheral clock cycle.

Set to select 12 clock periods per peripheral clock cycle.

4SIX2

Enhanced UART clock (MODE 0 and 2) (1)

Clear to select 6 clock periods per peripheral clock cycle.

Set to select 12 clock periods per peripheral clock cycle.

3T2X2

Timer2 clock (1)

Clear to select 6 clock periods per peripheral clock cycle.

Set to select 12 clock periods per peripheral clock cycle.

2T1X2

Timer1 clock (1)

Clear to select 6 clock periods per peripheral clock cycle.

Set to select 12 clock periods per peripheral clock cycle.

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 148 149

T89C51CC01 1

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