Rainbow Electronics T89C51RD2 - Manual (Page 23)

23 Rev. F - 15 February, 2001
T89C51RD2
Figure 7. PCA Timer/Counter
Table 7. CMOD: PCA Counter Mode Register
The CMOD SFR includes three additional bits associated with the PCA (See Figure 7 and Table 7).
•
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.
CMOD
Address 0D9H
CIDL WDTE - - - CPS1 CPS0 ECF
Reset value 0 0 X X X 0 0 0
Symbol Function
CIDL
Counter Idle control: CIDL = 0 programs the PCA Counter to continue functioning during
idle Mode. CIDL = 1 programs it to be gated off during idle.
WDTE
Watchdog Timer Enable: WDTE = 0 disables Watchdog Timer function on PCA Module 4.
WDTE = 1 enables it.
- Not implemented, reserved for future use. a
a. User software should not write 1s to reserved bits. These bits may be used in future 8051 family
products to invoke new features. In that case, the reset or inactive value of the new bit will be 0, and its
active value will be 1. The value read from a reserved bit is indeterminate.
CPS1 PCA Count Pulse Select bit 1.
CPS0 PCA Count Pulse Select bit 0.
CPS1 CPS0 Selected PCA input.
b
b. f
osc
= oscillator frequency
0 0 Internal clock f
osc
/12 ( Or f
osc
/6 in X2 Mode).
0 1 Internal clock f
osc
/4 ( Or f
osc
/2 in X2 Mode).
1 0 Timer 0 Overflow
1 1 External clock at ECI/P1.2 pin (max rate = f
osc
/ 8)
ECF
PCA Enable Counter Overflow interrupt: ECF = 1 enables CF bit in CCON to generate an
interrupt. ECF = 0 disables that function of CF.
CIDL CPS1 CPS0 ECF
It
CH CL
16 bit up/down counter
To PCA
modules
Fosc /12
Fosc / 4
T0 OVF
P1.2
Idle
CMOD
0xD9
WDTE
CF CR
CCON
0xD8
CCF4 CCF3 CCF2 CCF1 CCF0
overflow