Panasonic MN101C77C User Manual

Operation

Chapter 14    Automatic Transfer Controller

XIV - 13

13

„Data transfer modes

There are two types of ATC1 transfers, standard and burst, and sixteen transfer modes. Set the transfer

mode in ATC1 control register 0 (AT1CNT0).

„Standard and burst transfers

The ATC1 transfer modes are divided into standard transfer modes and burst transfer modes. There are

fourteen standard modes, 0 to D, and two burst modes, E and F.

In standard modes, the operation specified for that mode executes each time ATC1 is activated. When

the transfer ends, the value set in the transfer counter (AT1TRC) decrements and bus control returns to

the MCU core. This operation repeats until the transfer counter reaches x'00'. When this happens, ATC1

completes the final data transfer, then generates an interrupt (ATC1IRQ).

For instance, if the initial transfer counter value is x'05', and the ATC1 activation factor is set to a timer 0

interrupt, ATC1 is activated each time timer 0 overflows and the automatic transfer begins. After fifth

data transfers (activated by fifth timer 0 overflow) is complete, the transfer counter value becomes x'00',

an ATC1 interrupt occurs, and the operation ends. Timer 0 overflows occurring after this point do not

activate ATC1. For standard transfers, the program must set the transfer counter to the number of ATC1

activations required.

In burst modes, once ATC1 is activated, it transfers in one operation the number of bytes set in the

transfer counter (AT1TRC). After the burst transfer begins, the transfer counter decrements each time

ATC1 transfers one byte of data. When the counter reaches x'00', ATC1 generates an interrupt

(ATC1IRQ) and the burst transfer ends. For burst transfers, the program must set the transfer counter to

the number of data bytes in the burst transfer.

An external interrupt 0 can also be used to shut down ATC1 during a burst transfer. To enable this

function, set the burst transfer stop enable bit (BTSTP) in ATC1 control register 1 (AT1CNT1) to 1.

When BTSTP = 1, ATC1 data transfers stop when the external interrupt 0 interrupt request flag (IRQ0IR

flag in the IRQ0ICR register) is set. In an emergency shutdown, the transfer counter and memory pointer

save the values they contained prior to the shutdown. When the interrupt service routine ends, a new

activation factor restarts ATC1, and the burst transfer begins transferring data from the point at which it

stopped.

[           Table 14-1-2    Transfer Modes ]