AT89C51RE2 Atmel Corporation, AT89C51RE2 Datasheet - Page 84

• Manufacturer Part Number: AT89C51RE2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RE2

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Spi: 1
• Uart: 2
• Sram (kbytes): 8.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART/OCD
• Watchdog: Yes

84
AT89C51RE2
Table 54. CMOD Register
CMOD - PCA Counter Mode Register (D9h)
Reset Value = 00XX X000b
Not bit addressable
The CMOD register includes three additional bits associated with the PCA (See Figure 30 and
Table 54).
•
•
•
The CCON register contains the run control bit for the PCA and the flags for the PCA timer (CF)
and each module (Refer to Table 55).
•
•
•
Number
CIDL
The CIDL bit which allows the PCA to stop during idle mode.
The WDTE bit which enables or disables the watchdog function on module 4.
The ECF bit which when set causes an interrupt and the PCA overflow flag CF (in the CCON
SFR) to be set when the PCA timer overflows.
Bit CR (CCON.6) must be set by software to run the PCA. The PCA is shut off by clearing
this bit.
Bit CF: The CF bit (CCON.7) is set when the PCA counter overflows and an interrupt will be
generated if the ECF bit in the CMOD register is set. The CF bit can only be cleared by
software.
Bits 0 through 4 are the flags for the modules (bit 0 for module 0, bit 1 for module 1, etc.) and
are set by hardware when either a match or a capture occurs. These flags also can only be
cleared by software.
Bit
7
7
6
5
4
3
2
1
0
Mnemonic
WDTE
WDTE
CPS1
CPS0
CIDL
ECF
Bit
6
-
-
-
Description
Counter Idle Control
Cleared to program the PCA Counter to continue functioning during idle Mode.
Set to program PCA to be gated off during idle.
Watchdog Timer Enable
Cleared to disable Watchdog Timer function on PCA Module 4.
Set to enable Watchdog Timer function on PCA Module 4.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
PCA Count Pulse Select
CPS1 CPS0 Selected PCA input
0
0
1
1
PCA Enable Counter Overflow Interrupt
Cleared to disable CF bit in CCON to inhibit an interrupt.
Set to enable CF bit in CCON to generate an interrupt.
5
-
0
1
0
1
Internal clock fCLK PERIPH/6
Internal clock fCLK PERIPH/2
Timer 0 Overflow
External clock at ECI/P1.2 pin (max rate = fCLK PERIPH/ 4)
4
-
3
-
CPS1
2
CPS0
1
7663E–8051–10/08
ECF
0