6/11

UPGRADING FROM ST625X/6XB TO ST625X/6XC

set bit, datacopy

ld A, datacopy

ld DRA, A

1.2.2.2 Safe I/O State Switching Sequence

Switching the I/O ports from one state to another should be done in a sequence which ensures

that no unwanted side-effects can occur. The recommended safe transitions are illustrated in

Figure 4. All other transitions are potentially risky and should be avoided when changing the

I/O operating mode.

Figure 4. Diagram showing Safe I/O State Transitions

1.2.2.3 Handling Unused Port Bits

On ports that have less than 8 external pins connected:

– Leave the bits related to the unbonded pins in reset state and do not change their configu-

ration.

– Do not use instructions that act on a whole port register (INC, DEC, or read operations). Un-

available bits must be masked by software (AND instruction). Thus, when a read operation

performed on an incomplete port is followed by a comparison, use a mask.

1.2.3 8-bit Timer

On C revision devices, in order to use the 8-bit timer in gated mode, the PC1/TIM1 pin has to

be configured in input mode either with or without pull-up through the Port C DDR, OR and DR

registers.

On B revision devices, it was possible to define PC1/TIM1 pin as output in this mode. But on

C revision devices, if this pin is configured as output, the Schmitt trigger input is disabled and

the timer will therefore not work properly.

Interrupt

pull-up

Output

Open Drain

Output

Push-pull

Input

pull-up (Reset

state)

Input

Analog

Output

Open Drain

Output

Push-pull

Input

010*

000

100

110

011

001

101

111