AT89C5122D-RDRUM datasheet(68/208 Pages) ATMEL

68 / 208 page

AT83R5122, AT8xC5122/23

4202F–SCR–07/2008

When the WT counter times out, an interrupt is generated and the SCIB function is

locked: reception and emission are disabled. It can be enabled by resetting the macro or

reloading the counter.

The Waiting Time Counter can be used in T=0 protocol for the Work Waiting Time. It can

be used in T=1 protocol for the Character Waiting Time and for the Block Waiting Time.

See the detailed explanation below.

Figure 33.

Waiting Time Counter

In the so called manuel mode, the counter is loaded, if WTEN = 0, during the write of

SCWT2 register. The counter is loaded with a 32 bit word built with SCWT3 SCWT2

SCWT1 SCWT0 registers (SCWT0 contain WT[7-0] byte. WTEN is located in the

SCICR register.

When WTEN=1 and in UART mode, the counter is re-loaded at the occurence of a start

bit. This mode will be detailed below in T=0 protocol and T=1 protocol.

In manual mode, the WTEN signal controls the start of the counter (rising edge) and the

stop of the counter (falling edge). After a timeout of the counter, a falling edge on

WTEN, a reload of SCWT2 and a rising edge of WTEN are necessary to start again the

counter and to release the SCIB macro. The reload of SCWT2 transfers all SCWT0,

SCWT1, SCWT2 and SCWT3 registers to the WT counter.

In UART mode there is an automatic load on the start bit detection. This automatic load

is very useful for changing on-the-fly the timeout value since there is a register to hold

the load value. This is the case for T=1 protocol.

In T=0 protocol the maximun interval between the start leading edge of any character

sent by the ICC and the start of the previous character sent by either the ICC or the Ter-

minal is the maximum Work Waiting Time. The Work Waiting Time shall not exceed

960*D*WI ETUs with D and WI parameters are returned by the field TA1 and TC2

respectively in the Answer To Reset (ATR). This is the value the user shall write in the

SCWT0,1,2,3 register. This value will be reloaded in the Waiting Time counter every

start bit.

ETU Counter

WT Counter

Timeout

SCWT2

SCWT1

SCWT0

WT[31:0]

Load

WTEN

Start Bit

UART

Write_SCWT2

SCWT3

AT89C5122D-RDRUM Datasheet(PDF) 68 Page - ATMEL Corporation

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