Specifications

System Macros Invoked by Drivers
REQSCHAN
REQSCHAN
Obtains a secondary MASSBUS data channel.
Format
REQSCHAN [pri]
Parameter
[pri]
Priority of request. If the priority is HIGH, REQSCHAN calls
IOC$REQSCHANH; otherwise it calls IOC$REQSCHANL.
Description
The REQSCHAN macro calls IOC$REQSCHANH or IOC$REQSCHANL,
depending on the priority specified, to obtain a secondary MASSBUS data
channel.
When the REQSCHAN 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 REQSCHAN macro returns the address of the device’s CSR in R4 and
destroys the contents of R0 through R2.
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