IBM 1 Series - Functional Description of the DPC Adapter Signal Lines

Functional Description of the DPC Adapter Signal Lines
I/O Active
The DPC adapter has 75 lines that can have subsets, depending on the
level of functions required by the I/O device. Bits 1-3 and bits 4-7 of the
command field in the IDCB are mapped into DPC adapter function bits
(three bits) and modifier bits (four bits), respectively. Bits 12, 13, 14, and
15 of the device address field in the IDCB are mapped into the DPC
adapter device address bits. If the DPC adapter is configured for less than
16 I/O devices, bits 12 and 13 are truncated, as necessary, and replaced
by 0’s in the DPC adapter device address bits. Device addresses should
start at the lowest-configured device address. Figure 6-2 shows all the I/O
lines available between the DPC adapter and attached devices.
Signal Direction Number
name* (adapter/device) of lines
I/O active cece 1
Function bits a 3
Modifier bits ea 4
Device address TS 4
Data bus out ae 18 (16)**
Interrupt service active NN 1
Strobe Sua 1
Data bus in fee 18 (16)**
Interrupt request feos 16
Condition code in Se 3
Select response —_— 1
Halt or MCHK —— 1
System reset an 1
Power-on reset aan 1
Diagnostic mode ——— 1
1
Diagnostic mode modifi(r —_—_—_—_—_—"—>
* All signal lines are down-level active.
**When parity option is not selected.
Figure 6-2. DPC adapter signal lines
The DPC adapter signal tines are defined in the foilowing sections.
‘I/O active’ is an outbound tag to signal to an I/O device that it may
begin execution of the command specified by the function and modifier
bits. This tag is necessary to execute all device-directed commands. It is
active at least 200 nanoseconds after activation of the function, modifier,
and device-address bits.
Customer Direct Program Control (DPC) Adapter Feature 6-3