P8044AH-R0117 datasheet(44/65 Pages) INNOVASIC

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IA8044/IA8344

Data Sheet

SDLC Communications Controller

March 30, 2010

IA211010112-04

http://www.Innovasic.com

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UP (Unnumbered Poll) also called NSP, (Non-Sequenced Poll), or ORP (Optional

Response Poll)

In AUTO mode when the transmit buffer is full, the SIU can transmit an information frame when

polled for information. After transmission the SIU waits for acknowledgement from the receiving

station. If the response is positive, the SIU interrupts the CPU. If the response is negative, the

SIU retransmits the frame. The SIU can send the following responses to the primary station:

RR (Receive Ready)

RNR (Receive Not Ready)

The FLEXIBLE mode requires the CPU to control the SIU for both transmitting and receiving.

This slows response time but allows full SDLC and limited HDLC compatibility as well as

variations. In FLEXIBLE mode, the SIU can act as a primary station. The SIU will interrupt the

CPU after completion of a transmission without waiting for a positive acknowledgement from the

receiving station (see Table 46).

Table 46. Basic SDLC Frame

FLAG

ADDRESS

CONTROL

INFORMATION

FCS

FLAG

IA8044/IA8344 frame parameters:

Flag—8 bits

Address—8 bits

Control—8 bits

Information—n bytes (where n

192)

FCS—16 bits

Flag—8 bits

4.13

Frame Format Options

The various frame formats available with the IA8044/IA8344 are the standard SDLC format, the

no-control field format, the no-control field and no-address field formats, and the no-FCS field

format.

The standard SDLC format consists of an opening flag, an 8-bit address field, an 8-bit control

field, an n-byte information field, a 16-bit frame check sequence field, and a closing flag. The

FCS is generated by the CCIT-CRC polynomial (X16 + X12 + X5 + 1). The FCS is calculated on

the address, control, and information fields. The address and control fields may not be extended.

The address is contained in STAD and the control filed is contained in either RCB or TCB. This

format is supported by both AUTO and FLEXIBLE modes.

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