Teletypewriter Adapter Feature

Description

The Teletypewriter Adapter feature provides the circuitry necessary to attach a Teletype* Model ASR33/ ASR35, or equivalent to the channel of a Series/l processor. Any serial-by-bit device that meets the requirements of the adapter/device interface, and has one of the following bit-transfer rates, can also be attached:

Bits per second 50 75 100 110 150 200 300 600 1200

The interrupt mask time of the program support system used may preclude operation at these bit

2400 rates

4800 9600

Anyone of these bit rates can be selected by jumper options on the adapter feature card.

* Trademark of the Teletype Corporation

Some of the commercially available devices that can be attached to the adapter include:

• Printer-keyboards

• Keyboard-display units

• Keyboard-display-printer units Printers

Tape cassettes

• Tape units

• Card readers Badge readers

• Plotters

The teletypewriter adapter has a four-wire interface for data exchange between the adapter and the device (two for receive and two for transmit), and uses full-duplex operation (that is, data may be concurrently transmitted and received).

The data exchange across the adapter/device interface is not checked for parity or for any device-dependent control characters. The

teletypewriter adapter is code transparent, and all 256 binary combinations of a data byte can be transmitted and received; the adapter can also be configured for initial program load (IPL) operation.

Data transfer between the adapter and the Series/l processor is by byte, using direct program control (DPC) commands, except during IPL (when the transfer is by byte, using cycle-steal).

The teletypewriter adapter is packaged on a 4-wide, 6-high, printed-circuit card that may be plugged into any I/O slot in a Series/l processor or a 4959 I/O expansion unit. Certain adapter options require that

±

12 Vdc be available at the adapter card slot. These options are described in "Adapter Options" in this chapter. The ± 12 Vdc is not a standard feature on all Series/l processor types or models, or on the 4959 I/O expansion unit; however, the

±

12 Volt Communications Power feature is available, if required.

Teletypewriter Adapter Feature Card

Top-card cable connector

Customer cable

MSB LSB MSB LSB

MSB

LSB Primary Secondary

0 0 } Input selection

00 (refer to input

00 selection table)

I

Bit rate selection

00 (refer to bit-rate

00 selection table)

00 00

00 Device address selection

00 (a jumper installed means that

00 the corresponding device

00 address bit = logical 1)

00 00

}

IPL selection

00 (if no jumper is installed, the adapter

00 cannot perform IPL)

}

^Reserved

00 (these jumpers must not be installed)

A jumper installed equals a bit value of 1;

a jumper removed equals a bit value of O.

MSB = Most-significant bit LSB = Least-significant bit

Input selection table

MSB LSB I nput selected Input interpreted as 0 0 0 Contact sense Closed = data mark

a

1 TTL Minus = data mark

0 0 EIA Minus::: data mark

a

Internal wrap True data out

a a

Contact sense Open = data mark

a

TTL Plus = data mark

0 EIA Plus = data mark

Internal wrap True data out Bit rate selection table

MSB LSB Rate (bits per second)

a a

0 1

a a a a

a

0 0 0

a

0 1

a

0 0 0 1

0 0

a

^'1

a

50 75 100 110 150 200 300 600 1200 2400 4800 9600

Top-card cable

Top-card connector pin assignment A 1 Isolated receive input + A2 Current driver, current = mark

A3 Isolated receive input -, or isolated receive input + A4 EIA received data in

A5 Frame ground

A6 EIA data terminal ready

A& Solid state switch closed = data mark or minus {-I TTL data out A8 Solid state switch/TTL write control

B1 Nonisolated receive input -B2 Polarization

B3 Current driver, current = space B4 TTL received data in

B5 Signal ground B6 EIA transmitted data

B7 Solid state switch::: data mark, or plus (+') TTL data out B8 Solid state switch, TTL load control

Adapter Options

The adapter/device interface offers signal and bit-rate selection options to accommodate a wide range of attached devices. The options are selected by using the appropriate pins in the 16-pin top-card connector on the feature card, and/or jumpering of the selection pins on the feature card.

Adapter/Device Interface Input and Output Options Interface Input Options. The input options are:

Isolated contact sense * Open circuit = mark (logical 1) Closed circuit=mark

Non-isolated contact sense**

Open circuit=mark Closed circuit=mark

TTL (transistor-transistor logic) Plus level=mark

Minus level=mark

EIA (Electronics Industry Association)**

Minus level=mark (standard convention) Plus level=mark

* This option requires that the customer supply external power sources to drive the transmit and receive current loops.

* * These options require the ± 12 Volt Communications Power feature.

These input options are selected by utilizing the appropriate connector pins of the top-card connector on the feature card, and by jumper options on the feature card.

Inter/ace Output Options.

• Current driver*

Current=mark (logical 1) No current=mark

Solid state switch/TTL Closed/ minus= mark Open/ plus= mark BIA transmitted data*

Minus=mark (standard convention) EIA data terminal ready*

Active (on) when ± 12-volt feature is installed.

Solid state switch/TTL write control Solid state switch/TTL read control

* These options require the ± 12 Volt Communications Power feature.

The write- and read-control outputs are available for control of the user's attached device, and are

switched by modifier bit 7 of the Write and Read commands. These outputs are not used for the attachment of any standard teletypewriter I/O device.

The output options are selected by utilizing the appropriate pins of the top-card connector on the feature card.

Bit-Rate Option

Anyone of the 12 bit-transfer rates can be selected by installing the appropriate jumpers on the feature card.

Device-Address Option

The device address used by the Series/1 processor to communicate with the teletypewriter adapter is selected by jumpers that are located on the adapter feature card. Anyone of 256 device addresses (OO-FF hex) can be selected by installing the appropriate jumpers.

IPL Option

The teletypewriter adapter can be selected to perform initial program load (IPL), as either the primary or alternate IPL source, when the

appropriate jumper is installed on the feature card. If a jumper is not installed on either of the IPL source jumper pins, the adapter cannot be selected for IPL.

Teletypewriter Adapter Data Flow

" During a normal receive operation, data is received serially from the 'receive' line and is deserialized in the receive data register.

e

When a byte of data is accumulated in the receive data register, the byte is transferred to the receive buffer register, and an attention interrupt is generated in the adapter and presented to the pr()cessor.

• When the processor accepts the interrupt and issues a Read command to the adapter, the contents of the receive buffer register are gated to bits 8-15 of the processor 'data bus-in' lines.

Parity is generated as the data is sent to the processor.

E) During IPL operations, the data is gated to the processor in cycle-steal mode. After a byte of receive data is accumulated in the receive data register and moved to the receive buffer register, it is sent to the processor 'data bus-in' lines. The IPL storage address register (SAR) selects the data-bus byte (0-7 or 8-15) to which the receive data byte is gated. When SAR is even, the contents of the receive buffer register are gated to bits 0-7 of the 'data bus-in' lines. When SAR is odd, the data is gated to bits 8-15 of the 'data bus-in' lines. Parity is generated for each byte sent to the processor data bus.

e

For a transmit operation, the processor issues a Write command, which causes bits 8-15 of the processor 'data bus-out' lines to be loaded into the transmit data register. There, the data is serialized by shifting one bit at a time to the 'send' line (bit 15 is the first bit sent to the 'send' line).

o

The adapter's address compare logic samples each device address on the processor 'address bus-out' lines. The device address is compared with the device address jumpers on the adapter card, and, when an equal address compare occurs, the adapter is selected.

e

An equal address compare causes the adapter's command decode logic to decode bits 0-7 of the processor 'address bus-out' lines to determine the type of command. The command decode logic controls various gating lines that cause the adapter to execute the functions of the command.

Top-card connector

Receive line

*The buffered telet yp ewriter (TTY) ada ter p applies to processors with EC 755088 installed.

.. •

Channel

!

address bus receivers

Bits

" - - - 0-7

0

Address compare

Bits 8-15

--

--Device address jumpers

e ^e e

Receive Receive Channel

data buffer data bus Parity

1

bits 0-15, PO, P1 ^{Data bus}

-

.. • ^.. ..

- e

1

^Channel^{data bus} ^Transmit^data ^Top-card

Bits receivers register connector

8-15 IPL gating control

E)

lh-

Send line

Parity

l

checker

Address bus bits 0-16

..

^~ ^"4

..

e

^Channel

Command address bus

t

decode SAR for IPL drivers

Gating controls

Status bus bit 0

-Primary jumper

~L~

TTY adapter select

IPL controls

-

---~__:s~~---Status bus bit 1 Alternate 'umper

Data Transmit and Receive Operations

Data bytes are transmitted and received across the adapter/ device interface serially-by-bit with the least-significant bit being transmitted or received first. A start/stop frame of 10 or 11 bits is used for the data transfer. Each frame contains a start-bit, eight data-bits, and one or two stop-bits. Characters being transmitted by the teletypewriter adapter (to a device) are always followed by two stop-bits;

however, characters being received by the adapter (from a device) can have either one or two stop-bits.

Dans le document IBM Series/1 (Page 31-35)

Teletypewriter Adapter Feature

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