IBM 3745 Series, Hardware Maintenance Reference

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Basic Board Tail Gate
┌─ ── ── ── ── ── ── ── ─ ┐ │
│
│ ┌────────┐ ┌────────┐ │ │J1 AUI Cable ┌─────┐
│ CSP ├──┤ EAC \\\\\\\\\\\\i\\\\\\\\\\\i================== MAU ├───5
IOC │ │ Card │ │ Card │ │ ┌─────┐ │ │ └─────┘
Bus %────i───┤ │ │ │ ┌i─┤DC/DC├─┴─oGreen LED To Ethernet
│ │ │ │ +5V DC ─┤│ ├─ ─ ─┤+12V DC LAN Network
│ │ │ │ │ └i─┤DC/DC├─┬─oGreen LED
│ │ │ │ │ └─────┘ │ │ AUI Cable ┌─────┐
│ │ │ │ \\\\\\\\\\\\i\\\\\\\\\\\i================== MAU ├───5
└────────┘ └────┬───┘ │ │J2 └─────┘
DMA │ │ │
Bus %────i────────────────────┘ │ │
│
└─ ── ── ── ── ── ── ── ─ ┘ │
Up to two ELAs (coupled CSP/EAC cards) may be installed on the basic board, to
control up to four data links at one time.
On each EAC two data links to be connected at the tail gate to that EAC. Both
ports can be active at the same time.
Line Addressing
Each ELA supports a maximum of two line addresses.
With two possible ELAs, the maximum number of lines is four. Line numbers 1060
through 1063 are dedicated for ELA use.
The two lines associated with a particular ELA are addressed by the TD1 field of
the IOH. TD1 bit 6 selects one of the two lines. TD1 bit 7 selects either the
transmit or receive interface of the line. When TD1 bit 7 = 0 it selects the transmit
interface and when TD1 bit 7 = 1 it selects the receive interface.
Refer to “ESS Line Addressing” on page 3-45 for the mapping of the lines between
the boards and the tail gate.
12-6
IBM 3745 Models 130, 150, 160, 170, and 17A: Hardware Maintenance Reference