Specifications

System Macros Invoked by Drivers
REQPCHAN
REQPCHAN
Obtains a controller’s data channel.
Format
REQPCHAN [pri]
Parameters
[pri]
Priority of request. If the priority is HIGH, REQPCHAN calls
IOC$REQPCHANH; otherwise it calls IOC$REQPCHANL.
Description
The REQPCHAN macro calls IOC$REQPCHANH or IOC$REQPCHANL,
depending on the priority specified, to obtain a controller’s data channel.
When the REQPCHAN macro is invoked, the following registers must contain the
following values:
Register Contents
R5 Address of UCB
00(SP) Address of caller’s caller
The REQPCHAN macro returns the address of the device’s CSR in R4 and
destroys the contents of R0 through R2.
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